pipe-filter-gi, pipe-filter-ii: better use of 'inline'
* lib/pipe-filter-aux.c: New file.
* lib/pipe-filter-aux.h (PIPE_FILTER_AUX_INLINE): New macro.
Replace all uses of 'static inline' with it.
Use _GL_INLINE_HEADER_BEGIN, _GL_INLINE_HEADER_END.
* lib/pipe-filter-gi.c (filter_init, filter_cleanup)
(filter_retcode): No real need for inline here.
* modules/pipe-filter-gi, modules/pipe-filter-ii:
(Files): Add lib/pipe-filter-aux.c.
(Depends-on): Add extern-inline.
(configure.ac): Do not require AC_C_INLINE.
(lib_SOURCES): Add pipe-filter-aux.c.