Fix a docstring mistake: refer to os.execute, not os.system.
Fix a docstring mistake: refer to os.execute, not os.system.

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