Merge from trunk.

diff --cc ChangeLog
index 186331990081c494ab900b10a4f2761f3a5c1423,a7da9e1ad5bd593bb1922cff5300af773f181e40..95baf9c52947d6cae0f216217f265760eb50b8ad
--- 1/ChangeLog
--- 2/ChangeLog
+++ b/ChangeLog
@@@ -1,21 -1,3 +1,21 @@@
- 2012-04-17  Paul Eggert  <eggert@cs.ucla.edu>
++2012-04-18  Paul Eggert  <eggert@cs.ucla.edu>
 +
 +      configure: new option --enable-gcc-warnings (Bug#11207)
 +      I have been using this change for many months in my private copy
 +      of Emacs, and have used it to find several bugs.  It's mature
 +      enough to publish now.
 +      * Makefile.in (GNULIB_MODULES): Add warnings, manywarnings.
 +      * configure.in: Support --enable-gcc-warnings, in the style of
 +      other GNU packages such as coreutils.
 +      (C_WARNINGS_SWITCH): Remove, replacing with...
 +      (WARN_CFLAGS, GNULIB_WARN_CFLAGS): New variable.
 +      (PKG_CHECK_MODULES, C_SWITCH_X_SITE): Use -isystem rather than -I,
 +      when including system files with GCC.
 +      * etc/NEWS: Mention --enable-gcc-warnings.
 +      * INSTALL (DETAILED BUILDING AND INSTALLATION): Likewise.
 +      * lib/Makefile.am (AM_CFLAGS): New macro.
 +      * m4/manywarnings.m4, m4/warnings.m4: New files, from gnulib.
 +
  2012-04-17  Dmitry Antipov  <dmantipov@yandex.ru>
  
        * configure.in (AC_CHECK_FUNCS):

diff --cc lib-src/ChangeLog
index d8d0fc877b9eb28d362e2c832b73501c9f41f172,ea5f5a2662796092c11873f0c5b723b97ab5394e..106b2c8faca3149c56b56818dfbb88f894d35005
--- 1/lib-src/ChangeLog
--- 2/lib-src/ChangeLog
+++ b/lib-src/ChangeLog
@@@ -1,10 -1,3 +1,10 @@@
- 2012-04-17  Paul Eggert  <eggert@cs.ucla.edu>
++2012-04-18  Paul Eggert  <eggert@cs.ucla.edu>
 +
 +      configure: new option --enable-gcc-warnings (Bug#11207)
 +      * Makefile.in (C_WARNINGS_SWITCH): Remove.
 +      (WARN_CFLAGS, WERROR_CFLAGS): New macros.
 +      (BASE_CFLAGS): Use new macros rather than old.
 +
  2012-04-16  Paul Eggert  <eggert@cs.ucla.edu>
  
        Assume less-ancient POSIX support.

diff --cc lwlib/ChangeLog
index f6ffedeafda38a4f7a2aa019927cd0fb25559a14,8ac9e6994ab5fc92503cdcfe890dec4e6b1fe637..5451fa380013ccb3963a6df6ef0980364ddea715
--- 1/lwlib/ChangeLog
--- 2/lwlib/ChangeLog
+++ b/lwlib/ChangeLog
@@@ -1,10 -1,3 +1,10 @@@
- 2012-04-17  Paul Eggert  <eggert@cs.ucla.edu>
++2012-04-18  Paul Eggert  <eggert@cs.ucla.edu>
 +
 +      configure: new option --enable-gcc-warnings (Bug#11207)
 +      * Makefile.in (C_WARNINGS_SWITCH): Remove.
 +      (WARN_CFLAGS, WERROR_CFLAGS): New macros.
 +      (ALL_CFLAGS): Use new macros rather than old.
 +
  2012-04-11  Glenn Morris  <rgm@gnu.org>
  
        * Makefile.in (C_SWITCH_X_SYSTEM): Remove.

diff --cc msdos/ChangeLog
index bf3a11d5bd875d81312e288edc0615da4a349980,320d2f5e6c199b9626d7f0f3dc83ba838bd36cac..82f877eee9e998814c89a612770207053ce3636e
--- 1/msdos/ChangeLog
--- 2/msdos/ChangeLog
+++ b/msdos/ChangeLog
@@@ -1,9 -1,3 +1,9 @@@
- 2012-04-17  Paul Eggert  <eggert@cs.ucla.edu>
++2012-04-18  Paul Eggert  <eggert@cs.ucla.edu>
 +
 +      configure: new option --enable-gcc-warnings (Bug#11207)
 +      * sed1v2.inp, sed3v2.inp, sedlibmk.inp: GNULIB_WARN_CFLAGS,
 +      WARN_CFLAGS, and WERROR_CFLAGS replace C_WARNINGS_SWITCH.
 +
  2012-04-11  Glenn Morris  <rgm@gnu.org>
  
        * sedlibmk.inp, sed1v2.inp: GNUSTEP_CFLAGS replaces C_SWITCH_X_SYSTEM.

diff --cc oldXMenu/ChangeLog
index 243899e011d9385f5c302ed5992269841f700c92,5b86ccec21e8798696e2d9518a799f24d45a09a5..b1eb200416b1bfa0d5b22175f4605c59763c89ee
--- 1/oldXMenu/ChangeLog
--- 2/oldXMenu/ChangeLog
+++ b/oldXMenu/ChangeLog
@@@ -1,10 -1,3 +1,10 @@@
- 2012-04-17  Paul Eggert  <eggert@cs.ucla.edu>
++2012-04-18  Paul Eggert  <eggert@cs.ucla.edu>
 +
 +      configure: new option --enable-gcc-warnings (Bug#11207)
 +      * Makefile.in (C_WARNINGS_SWITCH): Remove.
 +      (WARN_CFLAGS, WERROR_CFLAGS): New macros.
 +      (ALL_CFLAGS): Use new macros rather than old.
 +
  2012-04-11  Glenn Morris  <rgm@gnu.org>
  
        * Makefile.in (C_SWITCH_X_SYSTEM): Remove.

diff --cc src/ChangeLog
index ae245a254a0ad60cecf7f42af358564831123509,2e3142b70150e0208273dfbac346fae32f26e602..ae91f04635b28f6963b7604b104300f1488db10f
--- 1/src/ChangeLog
--- 2/src/ChangeLog
+++ b/src/ChangeLog
@@@ -1,16 -1,3 +1,16 @@@
- 2012-04-17  Paul Eggert  <eggert@cs.ucla.edu>
++2012-04-18  Paul Eggert  <eggert@cs.ucla.edu>
 +
 +      configure: new option --enable-gcc-warnings (Bug#11207)
 +      * Makefile.in (C_WARNINGS_SWITCH): Remove.
 +      (WARN_CFLAGS, WERROR_CFLAGS): New macros.
 +      (ALL_CFLAGS): Use new macros rather than old.
 +      * process.c: Ignore -Wstrict-overflow to work around GCC bug 52904.
 +      * regex.c: Ignore -Wstrict-overflow.  If !emacs, also ignore
 +      -Wunused-but-set-variable, -Wunused-function, -Wunused-macros,
 +      -Wunused-result, -Wunused-variable.  This should go away once
 +      the Emacs and Gnulib regex code is merged.
 +      (xmalloc, xrealloc): Now static.
 +
  2012-04-17  Paul Eggert  <eggert@cs.ucla.edu>
  
        * dired.c (Fsystem_groups): Remove unused local.