Use C99-style 'extern inline' if available.

Use C99-style 'extern inline' if available.

* lib-src/profile.c (SYSTIME_INLINE): Define.
* nt/config.nt: Sync with autogen/config.in.
(_GL_INLINE, _GL_EXTERN_INLINE, _GL_INLINE_HEADER_BEGIN)
(_GL_INLINE_HEADER_END): New macros.
* src/buffer.h (BUFFER_INLINE):
* src/category.h (CATEGORY_INLINE):
* src/character.h (CHARACTER_INLINE):
* src/charset.h (CHARSET_INLINE):
* src/composite.h (COMPOSITE_INLINE):
* src/dispextern.h (DISPEXTERN_INLINE):
* src/lisp.h (LISP_INLINE):
* src/systime.h (SYSTIME_INLINE):
New macro, replacing 'static inline' in this header.
* src/buffer.h, src/category.h, src/character.h, src/charset.h:
* src/composite.h, src/dispextern.h, lisp.h, systime.h:
Use INLINE_HEADER_BEGIN, INLINE_HEADER_END.
* src/alloc.c (LISP_INLINE):
* src/buffer.c (BUFFER_INLINE):
* src/category.c (CATEGORY_INLINE):
* src/character.c (CHARACTER_INLINE):
* src/charset.c (CHARSET_INLINE):
* src/composite.c (COMPOSITE_INLINE):
* src/dispnew.c (DISPEXTERN_INLINE):
* src/sysdep.c (SYSTIME_INLINE):
Define to EXTERN_INLINE, so that the corresponding functions
are compiled into code.
* src/conf_post.h (INLINE, EXTERN_INLINE, INLINE_HEADER_BEGIN)
(INLINE_HEADER_END): New macros.
* src/lisp.h (PSEUDOVECTOR_FLAG): Now a macro as well as a constant,
since it's used in non-static inline functions now.