Bug #:

Submitted by:
Reviewed by:
- Added a getSourceRange() method to all subclasses of Expr.
- Changed all the constructors and instantiators.
- Only added SourceLocations's when necessary. For example, binary
expression *don't* carry the operator location...it isn't
necessary to implement getSourceRange(). On the other hand, unary
expressions *do* carry the operator location.
- Added trivial SourceRange value class to SourceLocation.

Note: need to talk to Chris about the FIXME for StringLiteral...
llvm-svn: 39452