Cache use of lang_get within loop on print_all_bug_page_word.php

This fixes a possible performance hit introduced in
94902e74c919f1341ab62a7c3b10f7b0ecf53689.

Cache the result of a lang_get() call once, and use the variable within
the loop. We don't want to make many expensive calls to lang_get() if it
can be avoided.