Refactor.

Refactor.

* gettext-tools/src/read-catalog-special.h: New file, extracted from
gettext-tools/src/read-catalog-abstract.h.
* gettext-tools/src/read-catalog-special.c: New file, extracted from
gettext-tools/src/read-catalog-abstract.c.
* gettext-tools/src/read-catalog-abstract.h (po_parse_comment_special): Remove
declaration.
* gettext-tools/src/read-catalog-abstract.c: Don't include <limits.h>.
(po_parse_comment_special): Moved to read-catalog-special.c.
* gettext-tools/src/Makefile.am (noinst_HEADERS): Add read-catalog-special.h.
(libgettextsrc_la_SOURCES): Add read-catalog-special.c.
* gettext-tools/src/FILES: Update.
* gettext-tools/libgettextpo/Makefile.am (libgettextpo_la_AUXSOURCES): Add
../src/read-catalog-special.c.