Add support for Motorola 88K to s_lock.h.

Apparently there are still people out there who care about this old
architecture.  They probably care about dusty versions of Postgres
too, so back-patch to all supported branches.

David Carlier (from a patch being carried by OpenBSD packagers)

Discussion: https://postgr.es/m/CA+XhMqzwFSGVU7MEnfhCecc8YdP98tigXzzpd0AAdwaGwaVXEA@mail.gmail.com

src/include/storage/s_lock.h

@@ -543,6 +543,30 @@ tas(volatile slock_t *lock)
 #endif	 /* (__mc68000__ || __m68k__) && __linux__ */
 
 
+/* Motorola 88k */
+#if defined(__m88k__)
+#define HAS_TEST_AND_SET
+
+typedef unsigned int slock_t;
+
+#define TAS(lock) tas(lock)
+
+static __inline__ int
+tas(volatile slock_t *lock)
+{
+	register slock_t _res = 1;
+
+	__asm__ __volatile__(
+		"	xmem	%0, %2, %%r0	\n"
+:		"+r"(_res), "+m"(*lock)
+:		"r"(lock)
+:		"memory");
+	return (int) _res;
+}
+
+#endif	 /* __m88k__ */
+
+
 /*
  * VAXen -- even multiprocessor ones
  * (thanks to Tom Ivar Helbekkmo)