[patch] [gdb/testsuite] Move start-of-function brace to handle Clang/GCC difference

[David Blaikie <dblaikie at gmail dot com>]

gdb.cp/cpexprs.exp is verifying behavior that's likely a GCC bug (GCC
PR60815 and some in person and IRC conversations with GCC developers).
GCC inconsistently places the prologue on either the line with the
function name or the line with the function's open brace. Clang
consistently uses the function's open brace.

Either these tests can be fixed by moving the line to break on and
XFAILing them all under GCC, or just making the test neutral to the
bug by moving the brace. I generally think it's best to just make the
test bug-neutral.

I've also had to update the .exp file to tolerate differences in the
type of vtable pointers (GCC's "const void ** const" versus Clang's
"void **") which required some refactoring.

Attachment: brace_location.diff
Description: Text document