Fix build on Win64

gcc thought that fourthFloating could be used without being defined.
In actual fact it couldn't, but I've refactored the code so that it
can now see this.

rts/Adjustor.c

@@ -491,22 +491,15 @@ createAdjustor(int cconv, StgStablePtr hptr,
 
     */
     {  
-        int i = 0;
-        int fourthFloating;
-        char *c;
         StgWord8 *adj_code;
 
         // determine whether we have 4 or more integer arguments,
         // and therefore need to flush one to the stack.
-        for (c = typeString; *c != '\0'; c++) {
-            i++;
-            if (i == 4) {
-                fourthFloating = (*c == 'f' || *c == 'd');
-                break;
-            }
-        }
+        if ((typeString[0] == '\0') ||
+            (typeString[1] == '\0') ||
+            (typeString[2] == '\0') ||
+            (typeString[3] == '\0')) {
 
-        if (i < 4) {
             adjustor = allocateExec(0x38,&code);
             adj_code = (StgWord8*)adjustor;
 
@@ -525,6 +518,9 @@ createAdjustor(int cconv, StgStablePtr hptr,
         }
         else
         {
+            int fourthFloating;
+
+            fourthFloating = (typeString[3] == 'f' || typeString[3] == 'd');
             adjustor = allocateExec(0x58,&code);
             adj_code = (StgWord8*)adjustor;
             *(StgInt32 *)adj_code        = 0x08ec8348;