patch to clear type mismatch warning in libiberty

[Jeffrey A Law]

  In message < Pine.OSF.3.96.970911151509.30251A-100000@ylws32 >you write:
  > The following patch clears type mismatch warning in libiberty.  It add
  > #include <string.h>
  > to files that need it.
  > 
  > Thu Sep 11 15:20:37 1997  Weiwen Liu  <liu@hepunix.physics.yale.edu>
  > 	* choose-temp.c: Add '#include <string.h>'.
  > 	* getopt.c: Ditto.
  > 	* xstrdup.c: Ditto.
Generally, including string.h or strings.h is discouraged in libiberty
since it is not autoconf'd and the availability of string/strings
varies greatly from one host system to another.

jeff