Better diagnostics from Sema::MergeFunctionDecl

As per Neil's comment:

http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20080114/003778.html

This patch ensures that function declarations are no longer called
definitions in the diagnostic output, which should be less confusing
for everybody :-).

Carl.

merge-func-decl.diff (3.48 KB)