libgettextpo: Remove static variables po_gram_lval, po_gram_char, po_gram_nerrs.
* gettext-tools/src/po-gram-gen.y: Request a pure parser.
* gettext-tools/src/po-lex.h (po_gram_lex): Add lval parameter.
* gettext-tools/src/po-lex.c (po_gram_lex): Add lval parameter. Store the result
in *lval instead of in po_gram_lval.
* gettext-tools/woe32dll/gettextsrc-exports.c: Remove po_gram_lval.