Fix spelling errors

src/powerpc/darwin_closure.S

@@ -192,7 +192,7 @@ LCFI1:
 	lg	r0,0(r3)		; size => r0
 	lhz	r3,FFI_TYPE_TYPE(r3)	; type => r3
 
-	/* The helper will have intercepted struture returns and inserted
+	/* The helper will have intercepted structure returns and inserted
 	   the caller`s destination address for structs returned by ref.  */
 
 	/* r3 contains the return type  so use it to look up in a table

src/powerpc/ffi.c

@@ -376,7 +376,7 @@ ffi_prep_args_SYSV (extended_cif *ecif, unsigned *const stack)
   FFI_ASSERT (gpr_base.u <= stacktop.u - ASM_NEEDS_REGISTERS);
   /* The assert below is testing that the number of integer arguments agrees
      with the number found in ffi_prep_cif_machdep().  However, intarg_count
-     is incremeneted whenever we place an FP arg on the stack, so account for
+     is incremented whenever we place an FP arg on the stack, so account for
      that before our assert test.  */
 #ifndef __NO_FPRS__
   if (fparg_count > NUM_FPR_ARG_REGISTERS)

src/powerpc/ffi_darwin.c

@@ -593,7 +593,7 @@ darwin_adjust_aggregate_sizes (ffi_type *s)
       /* Natural alignment for all items.  */
       align = p->alignment;
 #else
-      /* Natrual alignment for the first item... */
+      /* Natural alignment for the first item... */
       if (i == 0)
 	align = p->alignment;
       else if (p->alignment == 16 || p->alignment < 4)