Fix position of parsed applications

The end position was correctly set but the start position was wrong: the
start position of `fn(args)` should be the same as the start position of
`fn` itself.

Author: smarter

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -1533,7 +1533,7 @@ object Parsers {
       }
       if (in.token == LPAREN && (!inClassConstrAnnots || isLegalAnnotArg))
         parArgumentExprss(
-          atPos(in.offset) { Apply(fn, parArgumentExprs()) }
+          atPos(startOffset(fn)) { Apply(fn, parArgumentExprs()) }
         )
       else fn
     }

compiler/test-resources/repl/errmsgs

@@ -25,7 +25,7 @@ scala> val z: (List[String], List[Int]) = (List(1), List("a"))
   |
 scala> val a: Inv[String] = new Inv(new Inv(1))
 1 | val a: Inv[String] = new Inv(new Inv(1))
-  |                                  ^^^^^
+  |                                  ^^^^^^
   |                                  found:    Inv[Int]
   |                                  required: String
   |