Use stub implementations for get{e,}[ug]id

Use stub implementations for get{e,}[ug]id

These functions are unusable stubs today, indirectly via the
kludges that replace the syscall macros and stubs.  But on x86-32
they wind up as stubs that return 0 (false success) whereas on
x86-64 they fail with ENOSYS.  In neither case are they properly
marked as stubs so as to generate linker warnings, though in
neither case is there any mechanism by which they could be made
to do anything different.  Instead, just always use the basic
stub implementations that uniformly fail with ENOSYS and generate
linker warnings.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3667
TEST= toolchain trybots
R=dyen@chromium.org

Committed: https://git.chromium.org/gitweb?p=native_client/nacl-glibc.git;a=commit;h=9b15f6a

[David Yen, 2014-06-18 18:19:06]

lgtm

[Roland McGrath, 2014-06-18 18:41:35]

Committed patchset #1 manually as r9b15f6a (presubmit successful).