Fix Sema::ParseCallExpr()...it wasn't doing the default array/function promotions on it's argument types.

This resulted in the following errors when compiling promote_types_in_proto.c test...

[dylan:~/llvm/tools/clang] admin% ../../Debug/bin/clang test/Parser/promote_types_in_proto.c 
test/Parser/promote_types_in_proto.c:7:24: error: incompatible types passing 'char *[]' to function expecting 'char *const []'
        arrayPromotion(argv);
        ~~~~~~~~~~~~~~ ^~~~
test/Parser/promote_types_in_proto.c:8:27: error: incompatible types passing 'void (char *const [])' to function expecting 'void (char *const [])'
        functionPromotion(arrayPromotion);
        ~~~~~~~~~~~~~~~~~ ^~~~~~~~~~~~~~
2 diagnostics generated.

When fixing this, noticed that both ParseCallExpr() and ParseReturnStmt() were prematurely comparing types for
equivalence. This is incorrect (since the expr. promotions haven't been done yet). To fix this, I moved the
check "down" to Sema::CheckAssignmentConstraints().

I also converted Type::isArrayType() to the modern API (since I needed it). Still more Type predicates to 
convert.

llvm-svn: 40475