Improve error recovery in C/ObjC when the first argument of a function

declarator is incorrect.  Not being a typename causes the parser to 
dive down into the K&R identifier list handling stuff, which is almost
never the right thing to do.

Before:

r.c:3:17: error: expected ')'
void bar(intptr y);
                ^
r.c:3:9: note: to match this '('
void bar(intptr y);
        ^
r.c:3:10: error: a parameter list without types is only allowed in a function definition
void bar(intptr y);
         ^

After:

r.c:3:10: error: unknown type name 'intptr'; did you mean 'intptr_t'?
void bar(intptr y);
         ^~~~~~
         intptr_t
r.c:1:13: note: 'intptr_t' declared here
typedef int intptr_t;
            ^

This fixes rdar://7980651 - poor recovery for bad type in the first arg of a C function

llvm-svn: 103783