Added missing valid options for -langversion compiler option (#5371)

* Added missing valid options for -langversion compiler option

* Updated minimum compiler version section

* Removed duplicate text

* Updated ms.date

* Updated links to ECMA-334 editions

* Revert C#4.0 spec link

* Added Visual Studio 2017 versions

Author: pkulikov

docs/csharp/language-reference/compiler-options/langversion-compiler-option.md

@@ -1,6 +1,6 @@
 ---
 title: "-langversion (C# Compiler Options)"
-ms.date: 07/20/2015
+ms.date: 05/14/2018
 f1_keywords: 
   - "/langversion"
 helpviewer_keywords: 
@@ -32,12 +32,13 @@ Causes the compiler to accept only syntax that is included in the chosen C# lang
 |5|The compiler accepts only syntax that is included in C# 5.0 or lower <sup id="TCS5">[CS5](#FCS5)</sup>|
 |6|The compiler accepts only syntax that is included in C# 6.0 or lower <sup id="TCS6">[CS6](#FCS6)</sup>|
 |7|The compiler accepts only syntax that is included in C# 7.0 or lower <sup id="TCS7">[CS7](#FCS7)</sup>|
+|7.1|The compiler accepts only syntax that is included in C# 7.1 or lower <sup id="TCS71">[CS71](#FCS71)</sup>|
+|7.2|The compiler accepts only syntax that is included in C# 7.2 or lower <sup id="TCS72">[CS72](#FCS72)</sup>|
+|7.3|The compiler accepts only syntax that is included in C# 7.3 or lower <sup id="TCS73">[CS73](#FCS73)</sup>|
 |latest|The compiler accepts all valid language syntax that it can support. <sup id="TLatest">[Latest](#FLatest)</sup>|
+
 <!--- Uncomment and move these above
-|latest| once they're officially released
-|7.1|The compiler accepts only syntax that is included in C# 7.1 or lower <sup id="TCS71">[CS71](#FCS71)</sup>|
-|7.2|The compiler accepts only syntax that is included in C# 7.2 or lower <sup id="TCS71">[CS72](#FCS72)</sup>|
-|8|The compiler accepts only syntax that is included in C# 8 or lower <sup id="TCS71">[CS8](#FCS8)</sup>|
+|8|The compiler accepts only syntax that is included in C# 8 or lower <sup id="TCS8">[CS8](#FCS8)</sup>|
 -->
 
 
@@ -63,23 +64,21 @@ Causes the compiler to accept only syntax that is included in the chosen C# lang
  For information about how to set this compiler option programmatically, see <xref:VSLangProj80.CSharpProjectConfigurationProperties3.LanguageVersion%2A>.  
 
 ## See Also  
- [C# Compiler Options](../../../csharp/language-reference/compiler-options/index.md)  
+ [C# Compiler Options](index.md)  
  [Managing Project and Solution Properties](/visualstudio/ide/managing-project-and-solution-properties)  
 
 ### C# Language Specification
- [C# Language Specification Reference](../../../csharp/language-reference/language-specification/index.md) : .NET Foundation  
+ [C# Language Specification Reference](../language-specification/index.md) : .NET Foundation  
  C# 1.0/1.1 [ISO/IEC 23270:2003](https://www.iso.org/standard/36768.html) Information technology -- C# Language Specification : ISO Catalogue  
  C# 2.0 [ISO/IEC 23270:2006](https://www.iso.org/standard/42926.html) Information technology -- C# Language Specification : ISO Catalogue  
  C# 2.0 [c042926_ISO_IEC_23270_2006(E).zip](http://standards.iso.org/ittf/PubliclyAvailableStandards/c042926_ISO_IEC_23270_2006(E).zip) ISO/IEC 23270:2006 in PDF format : ISO Freely Available Standards  
  C# 3.0 [CSharp Language Specification.doc](http://download.microsoft.com/download/3/8/8/388e7205-bc10-4226-b2a8-75351c669b09/CSharp%20Language%20Specification.doc) C# Language Specification Version 3.0 : Microsoft Corporation  
  C# 4.0 [Ecma-334.pdf](https://www.ecma-international.org/publications/files/ECMA-ST/Ecma-334.pdf) Standard ECMA-334 4th Edition    
- C# 5.0 [CSharp Language Specification.docx](https://www.microsoft.com/download/details.aspx?id=7029) C# Language Specification Version 5.0 : Microsoft Corporation  
+ C# 5.0 [Ecma-334.pdf](https://www.ecma-international.org/publications/files/ECMA-ST/Ecma-334.pdf) Standard ECMA-334 5th Edition  
  C# 6.0 [README.md](https://github.com/dotnet/csharplang/blob/master/spec/README.md) C# Language Specification Version 6 - Unofficial Draft : .NET Foundation  
- C# 7.0 (not currently available)  
+ C# 7.0 and later (not currently available)  
 
 <!--- Uncomment and add to the above when they become officially released
- C# 7.1 (spec is not yet finished)  
- C# 7.2 (spec is not yet finished)  
  C# 8.0 (spec is not yet finished)  
 -->
 
@@ -90,10 +89,11 @@ Causes the compiler to accept only syntax that is included in the chosen C# lang
 [↩](#TCS4)<a name="FCS4">CS4</a>: Microsoft Visual Studio/Build Tools 2010 or bundled .Net Framework 4.0 compiler    
 [↩](#TCS5)<a name="FCS5">CS5</a>: Microsoft Visual Studio/Build Tools 2012 or bundled .Net Framework 4.5 compiler    
 [↩](#TCS6)<a name="FCS6">CS6</a>: Microsoft Visual Studio/Build Tools 2015    
-[↩](#TCS7)<a name="FCS7">CS7</a>, <a name="FLatest">Latest</a>: Microsoft Visual Studio/Build Tools 2017   
+[↩](#TCS7)<a name="FCS7">CS7</a>: Microsoft Visual Studio/Build Tools 2017   
+[↩](#TCS71)<a name="FCS71">CS71</a>: Microsoft Visual Studio/Build Tools 2017, version 15.3    
+[↩](#TCS72)<a name="FCS72">CS72</a>: Microsoft Visual Studio/Build Tools 2017, version 15.5    
+[↩](#TCS73)<a name="FCS73">CS73</a>, <a name="FLatest">Latest</a>: Microsoft Visual Studio/Build Tools 2017, version 15.7    
 
 <!--- Uncomment and add to the above when they become officially released
-[↩](#TCS71)<a name="FCS71">CS71</a>: Microsoft Visual Studio/Build Tools 20??    
-[↩](#TCS72)<a name="FCS72">CS72</a>: Microsoft Visual Studio/Build Tools 20??    
-[↩](#TCS8)<a name="FCS71">CS8</a>: Microsoft Visual Studio/Build Tools 20??    
+[↩](#TCS8)<a name="FCS8">CS8</a>: Microsoft Visual Studio/Build Tools 20??    
 -->