Fix some preprocessor warnings on Solaris.

Solaris is doing it wrong and polluting the global namespace
with register defines because the standard C/POSIX headers end
up including regset.h.

src/backend/code_x86.h

@@ -46,6 +46,11 @@ enum // #defining R12-R15 interfere with setjmps' _JUMP_BUFFER members
 /* There are also XMM8..XMM14 */
 #define XMM15   31
 
+/* See Solaris note in optabgen.c */
+#ifdef ES
+#undef ES
+#endif
+
 #define ES      24
 
 #define NUMGENREGS 16

src/backend/optabgen.c

@@ -724,9 +724,27 @@ void fltables()
 #endif
 
 /* Segment registers    */
+/* The #undefs are to appease the compiler on Solaris because
+   it, for some reason, ends up including regset.h in standard
+   C/POSIX headers, polluting the global namespace */
+#ifdef ES
+#undef ES
+#endif
 #define ES      0
+
+#ifdef CS
+#undef CS
+#endif
 #define CS      1
+
+#ifdef SS
+#undef SS
+#endif
 #define SS      2
+
+#ifdef DS
+#undef DS
+#endif
 #define DS      3
 
         for (i = 0; i < FLMAX; i++)