Auto-load safe-path and auto-load scripts-directory on Windows

[Eli Zaretskii]

> Date: Sat, 10 Oct 2015 09:39:50 +0800
> From: asmwarrior <asmwarrior@gmail.com>
> CC: gdb@sourceware.org
> 
> Maybe, this discussion is related:
> pkg-config wiki update and build problem - http://permalink.gmane.org/gmane.comp.gnu.mingw.msys/3822

That discussion is about a different problem, which we don't have in
GDB.  In GDB, the relevant character, DIRNAME_SEPARATOR, is computed
at compile time (not at configure time) in gdb/common/host-defs.h.

> Then, replace some text in the configure.ac:
> 
> AC_MSG_CHECKING([for default auto-load directory])
> AC_ARG_WITH(auto-load-dir,
> AS_HELP_STRING([--with-auto-load-dir=PATH],
>   [directories from which to load auto-loaded scripts @<:@$debugdir:$datadir/auto-load@:>@]),,
>   [with_auto_load_dir='$debugdir:$datadir/auto-load'])
> escape_dir=`echo $with_auto_load_dir | sed 's/[[$]]\(datadir\|debugdir\)\>/\\\\\\\\\\\\&/g'`
> AC_DEFINE_DIR(AUTO_LOAD_DIR, escape_dir,
> 	      [Directories from which to load auto-loaded scripts.])
> AC_MSG_RESULT([$with_auto_load_dir])

Patches to configure.ac to fix this problem are welcome.  I don't
think we need elaborate logic to compute the character, it's enough to
look at the host name.

Thanks.