* font.h (valid_font_driver) [!ENABLE_CHECKING]: Define a dummy.

This prevents a compilation error on C compilers that do not
default functions to return 'int' if not declared.  Also, add
INLINE_HEADER_BEGIN and INLINE_HEADER_END to this include file,
since it now uses inline functions.

src/ChangeLog

+2013-12-16  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* font.h (valid_font_driver) [!ENABLE_CHECKING]: Define a dummy.
+	This prevents a compilation error on C compilers that do not
+	default functions to return 'int' if not declared.  Also, add
+	INLINE_HEADER_BEGIN and INLINE_HEADER_END to this include file,
+	since it now uses inline functions.
+
 2013-12-16  Eli Zaretskii  <eliz@gnu.org>
 
 	* xdisp.c (extend_face_to_end_of_line): Don't fill background of

src/font.h

@@ -25,6 +25,8 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "ccl.h"
 #include "frame.h"
 
+INLINE_HEADER_BEGIN
+
 /* We have three types of Lisp objects related to font.
 
    FONT-SPEC
@@ -789,6 +791,12 @@ extern void register_font_driver (struct font_driver *driver, struct frame *f);
 extern void free_font_driver_list (struct frame *f);
 #ifdef ENABLE_CHECKING
 extern bool valid_font_driver (struct font_driver *);
+#else
+INLINE bool
+valid_font_driver (struct font_driver *d)
+{
+  return true;
+}
 #endif
 extern Lisp_Object font_update_drivers (struct frame *f, Lisp_Object list);
 extern Lisp_Object font_range (ptrdiff_t, ptrdiff_t, ptrdiff_t *,
@@ -862,4 +870,6 @@ extern void font_deferred_log (const char *, Lisp_Object, Lisp_Object);
       font_deferred_log ((ACTION), (ARG), (RESULT));	\
   } while (false)
 
+INLINE_HEADER_END
+
 #endif	/* not EMACS_FONT_H */