ia64: Switch places for the gate pages and the guard page. This improves

	backwards-compatibility with older (broken) versions of GCC which
	recognize a signal-handler only if it is in the address range
	from 0xa000000000000100. to 0xa000000000020000.

include/asm-ia64/system.h

@@ -19,8 +19,11 @@
 #include <asm/pal.h>
 #include <asm/percpu.h>
 
-/* 0xa000000000000000 - 0xa000000000000000+PERCPU_PAGE_SIZE remain unmapped */
-#define GATE_ADDR		(0xa000000000000000 + PERCPU_PAGE_SIZE)
+#define GATE_ADDR		(0xa000000000000000)
+/*
+ * 0xa000000000000000+2*PERCPU_PAGE_SIZE
+ * - 0xa000000000000000+3*PERCPU_PAGE_SIZE remain unmapped (guard page)
+ */
 #define KERNEL_START		 0xa000000100000000
 #define PERCPU_ADDR		(-PERCPU_PAGE_SIZE)