package/speechd: fix gettext version mismatch

- fix gettext version mismatch in case of BR2_SYSTEM_ENABLE_NLS and
  BR2_PACKAGE_PROVIDES_HOST_GETTEXT="host-gettext-gnu" by setting
  SPEECHD_GETTEXTIZE

Fixes:

  -  http://autobuild.buildroot.net/results/283333290c5adb48d0c6e592b3261992537f92d3



  Making all in po
  *** error: gettext infrastructure mismatch: using a Makefile.in.in from gettext version 0.19 but the autoconf macros are from gettext version 0.20

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>