Bugzilla bug #5358: temporary fix for the build problem on Solaris/x86.

We don't have an assembly language implementation of atomic stacks for
Solaris/x86 yet.  Thanks to Justin A. Kolodziej
<4wg7kolodzie@marquette.edu> for reporting the bug.

nsprpub/pr/include/md/_solaris.h

@@ -48,8 +48,14 @@
 #undef _PR_HAVE_ATOMIC_OPS
 #else
 #define _PR_HAVE_ATOMIC_OPS
+/*
+ * We have assembly language implementation of atomic
+ * stacks for the sparc architecture only.
+ */
+#ifdef sparc
 #define _PR_HAVE_ATOMIC_CAS
 #endif
+#endif
 
 #define _PR_POLL_AVAILABLE
 #define _PR_USE_POLL