Fixes for sparc-solaris2 configure

[Jeffrey A Law]

  In message < 199804061121.MAA06578@sun52.NIS.cambridge >you write:
  > This is a multipart MIME message.
  > 
  > --==_Exmh_16841231840
  > Content-Type: text/plain; charset=us-ascii
  > 
  > 
  > The following seems to have been lost during the recent xm-* configure.in 
  > changes:
  > 
  > <date>  Richard Earnshaw (rearnsha@arm.com)
  > 	* configure.in (sparc-*-solaris2*): Add xm-siglist.h to xm_file.
  > 	Add USG and POSIX to xm_defines.
Thanks, I've installed this patch into egcs.

jeff