[installer] add missing .pdb files to Xamarin.Android

Partially fixes: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1467817

A warning is printed when building with `-p:MonoSymbolArchive=true`:

    Warning: Directory obj\Release\120\android\assets contains Java.Interop.dll but no debug symbols file was found.

It turns out we are missing `Java.Interop.pdb` from our installer?

I went ahead and also added `Mono.Posix.pdb` and
`System.EnterpriseServices.pdb`, since we appear to have these in
build output.

Author: jonathanpeppers

build-tools/installers/create-installers.targets

@@ -134,10 +134,13 @@
     <_FrameworkFiles Include="@(MonoProfileAssembly->'$(FrameworkSrcDir)\$(BclFrameworkVersion)\%(Identity)')" />
     <_FrameworkFiles Include="@(MonoProfileAssemblySymbol->'$(FrameworkSrcDir)\$(BclFrameworkVersion)\%(Identity)')" />
     <_FrameworkFiles Include="$(FrameworkSrcDir)\$(BclFrameworkVersion)\Java.Interop.dll" />
+    <_FrameworkFiles Include="$(FrameworkSrcDir)\$(BclFrameworkVersion)\Java.Interop.pdb" />
     <_FrameworkFiles Include="$(FrameworkSrcDir)\$(BclFrameworkVersion)\Mono.Data.Sqlite.dll.config" />
     <_FrameworkFiles Include="$(FrameworkSrcDir)\$(BclFrameworkVersion)\Mono.Posix.dll" />
+    <_FrameworkFiles Include="$(FrameworkSrcDir)\$(BclFrameworkVersion)\Mono.Posix.pdb" />
     <_FrameworkFiles Include="$(FrameworkSrcDir)\$(BclFrameworkVersion)\RedistList\FrameworkList.xml" />
     <_FrameworkFiles Include="$(FrameworkSrcDir)\$(BclFrameworkVersion)\System.EnterpriseServices.dll" />
+    <_FrameworkFiles Include="$(FrameworkSrcDir)\$(BclFrameworkVersion)\System.EnterpriseServices.pdb" />
     <_FrameworkFiles Include="$(FrameworkSrcDir)\$(BclFrameworkVersion)\Xamarin.Android.NUnitLite.dll" />
     <_FrameworkFiles Include="$(FrameworkSrcDir)\$(BclFrameworkVersion)\Xamarin.Android.NUnitLite.pdb" />
     <_FrameworkFilesWin Include="$(FrameworkSrcDir)\$(FirstInstallerFrameworkVersion)\OpenTK-1.0.xml" />