Add CharSourceRange -- a half-open character range, which will be used in IDE

integration

Motivation: libIDE clients should be simple, and they should not have to
translate token-based SourceRanges to character locations.

This also allows us to remove the dependency of DiagnosticConsumer on the
Lexer.  Now the DiagnosticEngine translates the diagnostics to CharSourceRanges
and passes character-based ranges to the DiagnosticConsumer.


Swift SVN r7173

lib/Parse/ParseExpr.cpp

@@ -467,7 +467,7 @@ NullablePtr<Expr> Parser::parseExprUnary(Diag<> Message) {
 
     assert(OperEndLoc != Tok.getLoc() && "binary operator with no spaces?");
     diagnose(PreviousLoc, diag::expected_prefix_operator)
-      .fixItRemove(Diagnostic::Range(OperEndLoc, Tok.getLoc()));
+      .fixItRemoveChars(OperEndLoc, Tok.getLoc());
     break;
   }
   }