gcc/configure.in fix for 3.3 and 3.4

[Jim Wilson]

Gunther Nikl wrote:
> The attached patch for 3.3 and mainline removes $(XCFLAGS) from HOST/BUILD cflags
> when build != host. Its a fix for http://gcc.gnu.org/bugzilla/show_bug.cgi?id=10240

This was approved by Alexandre in the bug report.  I added the patch to 
mainline.  I did not add the patch to 3.3 because 3.3 is only open for 
regressions, and this is not a regression from 2.95.3.  XCFLAGS has 
apparently always been there.

Jim