meta: fix build with gettext 0.16.1

meta: fix build with gettext 0.16.1

The gettext 0.16.1 doesn't install any m4 files to sysroot, please see
the following commit:

  commit 9e10db5bdfe77c0ef2aff2f1cf89958b62c294a1
  Author: Christopher Larson <kergoth@gmail.com>
  Date:   Mon Mar 17 18:10:54 2014 +0000

      gettext-0.16.1: kill target m4 macros from sysroot

This is aim for using gettext-native's macros(gettext-native-0.19.4),
but when we set:
  PREFERRED_VERSION_gettext = "0.16.1"
And build the recipes like pcmanfm, we would get errors when
do_configure:

configure:5164: error: possibly undefined macro: AM_NLS

This is because autotools_copy_aclocals doesn't copy the native macros
for target unless they're direct dependencies.

inherit gettext will fix the problem.

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>