Fix for Clang 6.
Upstream commit 71852dae82445b5a43803e42897ccd0989d135ab.

Index: src/Unix/clip_unix.cpp
--- src/Unix/clip_unix.cpp.orig
+++ src/Unix/clip_unix.cpp
@@ -496,7 +496,7 @@ static void do_getscrap(void **handle, uint32 type, in
 			0x2f, 0x3c, 0, 0, 0, 0,		// move.l	#outbuf,-(sp)
 			0xa9, 0xfe,					// PutScrap()
 			0x58, 0x8f,					// addq.l	#4,sp
-			M68K_RTS >> 8, M68K_RTS
+			M68K_RTS >> 8, M68K_RTS & 0xff
 		};
 		r.d[0] = sizeof(proc);
 		Execute68kTrap(0xa71e, &r);		// NewPtrSysClear()
