Instead of reusing the input parameter to store the output, make a
result variable instead, so that there's less const confusion.

Fixes gcc warnings:
lcWrap.c: In function 'XSetLocaleModifiers':
lcWrap.c:87:18: warning: cast discards '__attribute__((const))' qualifier from pointer target type [-Wcast-qual]
lcWrap.c:91:25: warning: cast discards '__attribute__((const))' qualifier from pointer target type [-Wcast-qual]
lcWrap.c:93:12: warning: cast discards '__attribute__((const))' qualifier from pointer target type [-Wcast-qual]
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>