Make all current test cases pass in Darwin PowerPC.

* lib/jit_ppc-cpu.c: Make movr a function that checks arguments
	so that other code can safely assume it is a noop if src and dst
	are the same register.
	  Implement rem{r,i}{,_u} as a div{,u}/mul/sub.
	  Correct ANDIS, ORIS and XORIS calls to cast the argument to
	unsigned before the shift to avoid an assertion if the argument
	had the topmost bit set.
	  Implement lshi, rshi and rshi_u as functions to test for a
	zero argument, that would otherwise trigger an assertion when
	computing the shift value.
	  Do a simple implementation of bm{s,c}{r,i} with a temporary,
	"andr" of arguments and jump based on comparison with zero.
	  Correct typo in ldxi_c.

	* lib/jit_ppc-fpu.c: Correct wrong arguments to FDIV* and STF*.

	* lib/jit_ppc.c: Correct wrong check for 6 instead of 8 integer
	arguments in registers. If calling a varargs function and
	passing a float or double argument, also either store the
	value in the stack or in integer registers, as varargs functions
	do not fetch it from float registers.
	  Add "case" for new functions and incorrectly missing ones.
	  Call libgcc's __clear_cache, that should know what to do
	if the hardware needs flushing cache before execution.

	* lib/lightning.c: Do a simple/trivial logic in jit_regset_scan1,
	that should make it easier for the compiler to optimize it, and
	that also corrects the previously wrong code for big endian, and
	that was causing problems in ppc due to not saving all callee save
	registers as it was not "finding" them in the regset due to the
	little endian assumption bug.

lib/lightning.c

@@ -262,31 +262,10 @@ _jit_unget_reg(jit_state_t *_jit, jit_int32_t regno)
 unsigned long
 jit_regset_scan1(jit_regset_t set, jit_int32_t offset)
 {
-    jit_int32_t		index;
-    jit_int32_t		length;
-    union {
-	jit_uint64_t	ul;
-	jit_uint8_t	uc[8];
-    } data;
-
     assert(offset >= 0 && offset <= 63);
-    data.ul = set;
-    if (data.uc[index = offset >> 3]) {
-	length = (index + 1) << 3;
-	for (; offset < length; offset++) {
-	    if (set & (1LL << offset))
-		return (offset);
-	}
-    }
-    for (index++; index < 8; index++) {
-	if (data.uc[index]) {
-	    offset = index << 3;
-	    length = (index + 1) << 3;
-	    for (; offset < length; offset++) {
-		if (set & (1LL << offset))
-		    return (offset);
-	    }
-	}
+    for (; offset < 64; offset++) {
+	if (set & (1LL << offset))
+	    return (offset);
     }
     return (ULONG_MAX);
 }