libgettextpo: Remove static variable error_with_progname, part 2.
* gettext-tools/src/read-po-lex.h: Don't include error-progname.h.
* gettext-tools/src/format-scheme.c: Likewise.
* gettext-tools/src/read-desktop.c: Likewise.
* gettext-tools/src/x-desktop.c: Likewise.