xgettext: Handle newlines in Lua long bracket literal strings correctly.
Reported by Frans de Jonge <fransdejonge@gmail.com>
at <https://savannah.gnu.org/bugs/?56794>.
* gettext-tools/src/x-lua.c (phase3_get): Test for EOF first. After an opening
long bracket, swallow one newline.
* gettext-tools/tests/xgettext-lua-1: Add tests for newlines in long brackets.
* gettext-tools/tests/xgettext-lua-2: Update comment.
