Add x86 (32-bit) sret trampoline.

Test/BlockImpTest.m

@@ -1,11 +1,18 @@
 #include <objc/runtime.h>
 #include <objc/blocks_runtime.h>
 #include <assert.h>
+#include <stdio.h>
+
+struct big
+{
+	int a, b, c, d, e;
+};
 
 @interface Foo @end
 @implementation Foo @end
 @interface Foo (Dynamic)
 +(int)count: (int)i;
++(struct big)sret;
 @end
 
 int main(void)
@@ -22,5 +29,16 @@ int main(void)
 	assert(6 == [Foo count: 2]);
 	assert(imp_getBlock(imp) == (blk));
 	imp_removeBlock(blk);
+
+	blk = ^(id self) {
+		struct big b = {1, 2, 3, 4, 5};
+		return b;
+	};
+	imp = imp_implementationWithBlock(blk);
+	char *type;
+	asprintf(&type, "%s@:", @encode(struct big));
+	class_addMethod((objc_getMetaClass("Foo")), @selector(sret), imp, type);
+	struct big s = [Foo sret];
+	fprintf(stderr, "%d %d %d %d %d\n", s.a, s.b, s.c, s.d, s.e);
 	return 0;
 }

block_trampolines.S

@@ -40,6 +40,14 @@ next_line:
 	jmp   *-13(%eax)           # Call the block function
 __objc_block_trampoline_end:
 __objc_block_trampoline_sret:
+	call  next_line2           # Store the instruction pointer on the stack
+next_line2:
+	pop   %eax                 # Load the old instruction pointer
+	mov   8(%esp), %ebx        # Load the self parameter
+	mov   %ebx, 12(%esp)        # Store self as the second argument
+	mov   -9(%eax), %ebx       # Load the block pointer to %ebx
+	mov   %ebx, 8(%esp)        # Store the block pointer in the first argument
+	jmp   *-13(%eax)           # Call the block function
 __objc_block_trampoline_end_sret:
 #else
 __objc_block_trampoline: