Switch cache-long-scans to t by default.

 src/xdisp.c (message_dolog): Make sure the *Messages* buffer has its
 cache-long-scans disabled, since we don't want to call
 prepare_to_modify_buffer (in insert_1_both) for each message we
 display.
 src/buffer.h (bset_cache_long_scans): New INLINE function, moved
 from buffer.c.  Improve commentary to the buffer field setter
 functions.
 src/buffer.c (bset_cache_long_scans): Static function deleted.
 Improve commentary to the buffer field setter functions.
 (init_buffer_once): Default for cache-long-scans changed to t.
 (Bug#15797)

1 files changed, 7 insertions, 1 deletions

diff --git a/src/buffer.h b/src/buffer.h
index a36c0d13c9e..f39e3d33185 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -871,13 +871,19 @@ struct buffer
 };
 
 /* Most code should use these functions to set Lisp fields in struct
-   buffer.  */
+   buffer.  (Some setters that are priviate to a single .c file are
+   defined as static in those files.)  */
 INLINE void
 bset_bidi_paragraph_direction (struct buffer *b, Lisp_Object val)
 {
   b->INTERNAL_FIELD (bidi_paragraph_direction) = val;
 }
 INLINE void
+bset_cache_long_scans (struct buffer *b, Lisp_Object val)
+{
+  b->INTERNAL_FIELD (cache_long_scans) = val;
+}
+INLINE void
 bset_case_canon_table (struct buffer *b, Lisp_Object val)
 {
   b->INTERNAL_FIELD (case_canon_table) = val;