posix: fix gettimeofday LDocs to match API.
posix: fix gettimeofday LDocs to match API.

Fix #133.
* ext/posix/posix.c (Pgettimeofday): Has returned a Lua table
with `sec` and `usec` fields for quite some time... make sure
the LDocs reflect that!

Signed-off-by: Gary V. Vaughan <f9023000f29773649f3850298becb9544b5fd6a9@gnu.org>

jimmyharris/luaposix,ardje/luaposix,ardje/luaposix,zevv/luaposix,snegovick/luaposix,rrthomas/luaposix,rrthomas/luaposix,zevv/luaposix,snegovick/luaposix,luaposix/luaposix,jimmyharris/luaposix