VG_(get_fnname_kind): Recognize gcc "optimized" below main functions.

VG_(get_fnname_kind): Recognize gcc "optimized" below main functions.

The VG_(get_fnname_kind) function detects some special "below main"
function names. Specifically __libc_start_main and generic_start_main
both of which are used to call the actual main () function from the
application. We already recognized one variant, generic_start_main.isra.0,
but only for powerpc. Recognize all possibly specialed optimized variants
gcc can produce by simply checking for the function name with dot as
prefix. This fixes the memcheck/tests/supp_unknown.vgtest and
massif/tests/deep-D.vgtest with gcc 11.

We can now also get rid of the special cases in
massif/tests/deep-D.post.exp-ppc64 and memcheck/tests/supp_unknown.supp.

https://bugs.kde.org/show_bug.cgi?id=430158