Fixup commit 39b83981 ("Flush icache with __builtin___clear_cache() in
tests when compiling with GCC") to fix compilation with older GCC
versions that do not provide __builtin___clear_cache().
When compiling with GCC, use the builtin instruction cache flushing
mechanism in all tests where it is needed.
Quoting GCC docs: ''If the target does not require instruction cache
flushes, __builtin___clear_cache has no effect. Otherwise either
instructions are emitted in-line to clear the instruction cache or a
call to the __clear_cache function in libgcc is made.''.
(main): Send SIGUSR1 before dynamic testing starts, SIGUSR2 afterwards (makes it
easy for test-ptrace to catch when verification should begin).
Add test case for func_vframe().
(Logical change 1.56)
