xgettext: In language JavaScript, avoid a crash.
This avoids a crash
"Assertion `phase2_pushback_length + j < SIZEOF (phase2_pushback)' failed.".
* gettext-tools/src/x-javascript.c (phase2_pushback): Increase size by 1.
* gettext-tools/tests/xgettext-javascript-12: New file.
* gettext-tools/tests/Makefile.am (TESTS): Add it.
