Add load-prefer-newer option, to load .el if newer than .elc

* src/lread.c (Fload): Pass load_prefer_newer to openp.
Don't bother checking mtime if openp already did it.
(openp): Add `newer' argument, to check all suffixes
and find the newest file.
(syms_of_lread) <load_prefer_newer>: New option. 

* src/callproc.c (call_process):
* src/charset.c (load_charset_map_from_file):
* src/emacs.c (init_cmdargs):
* src/image.c (x_create_bitmap_from_file, x_find_image_file):
* src/lisp.h (openp):
* lread.c (Flocate_file_internal):
* src/process.c (Fformat_network_address):
* src/sound.c (Fplay_sound_internal):
* src/w32.c (check_windows_init_file):
* src/w32proc.c (sys_spawnve): Update for new arg spec of openp.

* lisp/Makefile.in (BYTE_COMPILE_FLAGS): Set load-prefer-newer to t.

* etc/NEWS: Mention this.

Fixes: debbugs:2061

3 files changed, 9 insertions, 1 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 126f10ae79b..435581799b6 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,7 @@
+2013-12-18  Glenn Morris  <rgm@gnu.org>
+
+        * Makefile.in (BYTE_COMPILE_FLAGS): Set load-prefer-newer to t.
+
 2013-12-18  Le Wang  <l26wang@gmail.com>
 
         * comint.el (comint-previous-matching-input-from-input): Retain
@@ -9,6 +13,8 @@
 
 2013-12-18  Glenn Morris  <rgm@gnu.org>
 
+        * cus-start.el (load-prefer-newer): New option.
+
         * mail/emacsbug.el (report-emacs-bug):
         Only mention enable-multibyte-characters if non-standard.
 
diff --git a/lisp/Makefile.in b/lisp/Makefile.in
index 2ac2f3e8d6b..39452edcbf4 100644
--- a/lisp/Makefile.in
+++ b/lisp/Makefile.in
@@ -88,7 +88,8 @@ AUTOGEN_VCS = \
 BIG_STACK_DEPTH = 2200
 BIG_STACK_OPTS = --eval "(setq max-lisp-eval-depth $(BIG_STACK_DEPTH))"
 
-BYTE_COMPILE_FLAGS = $(BIG_STACK_OPTS) $(BYTE_COMPILE_EXTRA_FLAGS)
+# Set load-prefer-newer for the benefit of the non-bootstrappers.
+BYTE_COMPILE_FLAGS = $(BIG_STACK_OPTS) --eval '(setq load-prefer-newer t)' $(BYTE_COMPILE_EXTRA_FLAGS)
 
 # Files to compile before others during a bootstrap.  This is done to
 # speed up the bootstrap process.  They're ordered by size, so we use
diff --git a/lisp/cus-start.el b/lisp/cus-start.el
index 8e94e85f84c..32013b71125 100644
--- a/lisp/cus-start.el
+++ b/lisp/cus-start.el
@@ -312,6 +312,7 @@ Leaving \"Default\" unchecked is equivalent with specifying a default of
              ;;                         :format "%[Current dir?%] %v"
              ;;                         (const :tag " current dir" nil)
              ;;                         (directory :format "%v"))))
+             (load-prefer-newer lisp boolean "24.4")
              ;; minibuf.c
              (enable-recursive-minibuffers minibuffer boolean)
              (history-length minibuffer