Add a rule for sdl ldl $1==$2 to work around a bug.

In our powerpc table, sdl fails to kill the old value of the local.
This is a bug, because a later ldl can load the old value instead of
the newly stored value.  By rewriting "sdl 0" "ldl 0" as "dup 8" "sdl
0", the newly added rule works around the bug, but only when the ldl
is immediately after the sdl.

This rule improves code that uses double-precision floating point.
The output of printf("%f", 6.0) in C changes from all zero digits to
"6000000" but still doesn't print the decimal point.  The result of
atof("-123.456") becomes correct.  In startrek, I can now move the
Enterprise, but I still can't fire phasers without crashing the game.

We already have a rule for stl lol $1==$2.  We had two copies of the
rule, so I am deleting the second copy.

mach/powerpc/ncg/table

@@ -923,10 +923,14 @@ PATTERNS
 	pat dup $1==INT32                  /* Duplicate word on top of stack */
 		with GPR
 			yields %1 %1
+		with FSREG
+			yields %1 %1
 								
 	pat dup $1==INT64                  /* Duplicate double-word on top of stack */
 		with GPR GPR
 			yields %2 %1 %2 %1
+		with FREG
+			yields %1 %1
 								
 	pat exg $1==INT32                  /* Exchange top two words on stack */
 		with GPR GPR
@@ -937,6 +941,11 @@ PATTERNS
 			dup 4
 			stl $1
 
+	pat sdl ldl $1==$2                 /* Store then load double local */
+		leaving
+			dup 8
+			sdl $1
+
 	pat lal sti lal loi $1==$3 && $2==$4 /* Store then load local, of a different size */
 		leaving
 			dup INT32
@@ -1046,11 +1055,6 @@ PATTERNS
 			lol $1
 			sti INT32
 
-	pat stl lol $1==$2                 /* Save then load (generated by C compiler) */
-		leaving
-			dup 4
-			stl $1
-			
 	pat zrl                             /* Zero local */
 		leaving
 			loc 0