libbacktrace: load Windows modules

Patch from Björn Schäpers <bjoern@hazardy.de>.

	* configure.ac: Checked for tlhelp32.h
	* pecoff.c: Include <tlhelp32.h> if available.
	(backtrace_initialize): Use tlhelp32 api for a snapshot to
	detect loaded modules.
	(coff_add): New argument for the module handle of the file,
	to get the base address.
	* configure, config.h.in: Regenerate.

configure.ac

@@ -374,6 +374,10 @@ if test "$have_loadquery" = "yes"; then
 fi
 
 AC_CHECK_HEADERS(windows.h)
+AC_CHECK_HEADERS(tlhelp32.h, [], [],
+[#ifdef HAVE_WINDOWS_H
+#  include <windows.h>
+#endif])
 
 # Check for the fcntl function.
 if test -n "${with_target_subdir}"; then