Fix invocation of Windows batch files with whitespace in their names.

Fix invocation of Windows batch files with whitespace in their names.

 w32/subproc/sub_proc.c: Include makeint.h.  Remove a private
 incompatible prototype of xmalloc.
 (batch_file_with_spaces): New function, detects Windows batch
 files whose names include whitespace characters.
 (process_begin): If exec_name is a batch file with whitespace
 characters in its name, pass NULL as the first argument to
 CreateProcess.  This avoids weird failures due to buggy quoting by
 CreateProcess.  For the details, see the discussion starting at
 http://lists.gnu.org/archive/html/make-w32/2013-04/msg00008.html.