[BZ #15897] dlfcn: do not mark dlopen/dlclose as leaf functions

[BZ #15897] dlfcn: do not mark dlopen/dlclose as leaf functions

Since the dlopen funcs might invoke a constructor that calls a func
that is in the same compilation unit as the caller, we cannot mark
them as leaf funcs.

Similarly, dlclose might invoke a destructor that calls a func that
is in the same compilation unit as the caller.

URL: https://sourceware.org/bugzilla/show_bug.cgi?id=15897
Reportedy-by: Fabrice Bauzac <libnoon@gmail.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>