Support for target descriptions layered on top of sparc32/sparc64
which describe more registers than native ones.
Pseudo registers always come after the real registers.
One more step forward to modernize sparc tdep's.
Submitted to upstream as:
https://sourceware.org/bugzilla/show_bug.cgi?id=20936

--- gdb-7.11/gdb/sparc64-tdep.h.orig	2016-11-13 21:26:01.870566687 -0800
+++ gdb-7.11/gdb/sparc64-tdep.h	2016-11-13 21:26:21.157185579 -0800
@@ -56,8 +56,11 @@
   SPARC64_FSR_REGNUM,		/* %fsr */
   SPARC64_FPRS_REGNUM,		/* %fprs */
   SPARC64_Y_REGNUM,		/* %y */
+};
 
-  /* Pseudo registers.  */
+/* Pseudo registers.  */
+enum sparc64_pseudo_regnum
+{
   SPARC64_CWP_REGNUM,		/* %cwp */
   SPARC64_PSTATE_REGNUM,	/* %pstate */
   SPARC64_ASI_REGNUM,		/* %asi */