Really fix sgen on PowerPC Linux. Assembler on Linux requires that register...

Really fix sgen on PowerPC Linux. Assembler on Linux requires that register names are just bare numbers, unlike OSX, i.e. "r0" must be "0" on Linux.

mono/metadata/sgen-archdep.h

@@ -107,12 +107,21 @@
 #define REDZONE_SIZE	224
 
 #define ARCH_NUM_REGS 32
+#ifdef __APPLE__
 #define ARCH_STORE_REGS(ptr)	\
 	__asm__ __volatile__(	\
 		"stmw r0, 0(%0)\n"	\
 		:			\
 		: "b" (ptr)		\
 	)
+#else
+#define ARCH_STORE_REGS(ptr)	\
+	__asm__ __volatile__(	\
+		"stmw 0, 0(%0)\n"	\
+		:			\
+		: "b" (ptr)		\
+	)
+#endif
 #define ARCH_SIGCTX_SP(ctx)	(UCONTEXT_REG_Rn((ctx), 1))
 #define ARCH_SIGCTX_IP(ctx)	(UCONTEXT_REG_NIP((ctx)))
 #define ARCH_COPY_SIGCTX_REGS(a,ctx) do {	\