Fix PR7617 by not entering ParseFunctionDefinition when

Fix PR7617 by not entering ParseFunctionDefinition when
a function prototype is followed by a declarator if we
aren't parsing a K&R style identifier list.

Also, avoid skipping randomly after a declaration if a
semicolon is missing.  Before we'd get:

t.c:3:1: error: expected function body after function declarator
void bar();
^

Now we get:

t.c:1:11: error: invalid token after top level declarator
void foo()
          ^
          ;

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108105 91177308-0d34-0410-b5e6-96231b3b80d8