[RFA/gdb-7.2] Enable leading-mingw64-underscores by default.

[Joel Brobecker <brobecker at adacore dot com>]

There has been a recent ABI change made in GCC for x64-windows, and
the corresponding change was made in binutils/GCC at the same time.
This change must be synchronized between GCC & GDB, because they must
both follow the same convention.

While this change was made, and backward-compatibility switch was
added: --enable-leading-mingw64-underscores.

Until we have a GCC release containing that ABI change (scheduled for
GCC 4.5.1), I think it is more helpful for this GDB release to assume
the old ABI.

This patch changes the configure script to make this new option the
default when not specified. GDB can still be configured by using
--disable-leading-mingw64-underscores.

Note that this patch enables this compatibility feature by default
on all platforms and for all targets. I think that this is the right
thing to do, because this only affects the COFF/PE64 object file
which is independent from host/target.

Tested on x86_64-windows by configuring bfd with and without the patch,
with and without --enable/disable-leading-mingw64-underscores, and
inspecting the contents of bfd/config.h. For kicks, I'm also testing
this change on x86_64-linux, although I don't expect any change there.

bfd/ChangeLog:

        * configure.in: Make --enable-leading-mingw64-underscores
        the default.
        * configure: Regenerate.

Thoughts? Yay? Nay?

Thanks,
-- 
Joel

---
 bfd/configure    |    2 ++
 bfd/configure.in |    2 +-
 2 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/bfd/configure b/bfd/configure
index 51a4158..6736940 100755
--- a/bfd/configure
+++ b/bfd/configure
@@ -12062,6 +12062,8 @@ fi
 # Check whether --enable-leading-mingw64-underscores was given.
 if test "${enable_leading_mingw64_underscores+set}" = set; then :
   enableval=$enable_leading_mingw64_underscores;
+else
+  enable_leading_mingw64_underscores="yes"
 fi
 
 if  test x"$enable_leading_mingw64_underscores" = xyes ; then :
diff --git a/bfd/configure.in b/bfd/configure.in
index 13fb66f..6ec3614 100644
--- a/bfd/configure.in
+++ b/bfd/configure.in
@@ -78,7 +78,7 @@ fi
 AC_ARG_ENABLE(leading-mingw64-underscores,
   AS_HELP_STRING([--enable-leading-mingw64-underscores],
                  [Enable leading underscores on 64 bit mingw targets]),
-  [],[])
+  [],[enable_leading_mingw64_underscores="yes"])
 AS_IF([ test x"$enable_leading_mingw64_underscores" = xyes ],
   [AC_DEFINE(USE_MINGW64_LEADING_UNDERSCORES, 1,
     [Define if we should use leading underscore on 64 bit mingw targets])])
-- 
1.7.1