cdecl calling convention expects the callee to pop the hidden pointer on

struct return. For example, GCC and LLVM comply with this (tested on IA32).

ACK doesn't seem to follow this convention and expects the caller to clean up
the stack. Compiling hand-written ACK-compliant assembly code (returning a 
struct) with GCC or LLVM used to break things (4-bytes misaligned stack).

The patch fixes this problem.

lib/libc/arch/i386/int64/add64.S

@@ -1,5 +1,7 @@
 /*	add64() - 64 bit addition			Author: Kees J. Bot */
 /*								7 Dec 1995 */
+#include <minix/compiler.h>
+
 .text
 .globl	_add64
 
@@ -12,7 +14,7 @@ _add64:
 	movl	12(%esp), %edx
 	adcl	20(%esp), %edx
 	movl	%edx, 4(%eax)
-	ret
+	ret BYTES_TO_POP_ON_STRUCT_RETURN
 
 /* */
 /* $PchId: add64.ack.s,v 1.2 1996/04/11 18:59:57 philip Exp $ */

lib/libc/arch/i386/int64/add64u.S

@@ -1,5 +1,7 @@
 /*	add64u() - unsigned to 64 bit addition		Author: Kees J. Bot */
 /*								7 Dec 1995 */
+#include <minix/compiler.h>
+
 .text
 .globl	_add64u, _add64ul
 
@@ -14,7 +16,7 @@ _add64ul:
 	movl	12(%esp), %edx
 	adcl	$0, %edx
 	movl	%edx, 4(%eax)
-	ret
+	ret BYTES_TO_POP_ON_STRUCT_RETURN
 
 /* */
 /* $PchId: add64u.ack.s,v 1.2 1996/04/11 18:59:57 philip Exp $ */

lib/libc/arch/i386/int64/cvu64.S

@@ -1,5 +1,7 @@
 /*	cvu64() - unsigned converted to 64 bit		Author: Kees J. Bot */
 /*								7 Dec 1995 */
+#include <minix/compiler.h>
+
 .text
 .globl	_cvu64, _cvul64
 
@@ -11,7 +13,7 @@ _cvul64:
 	movl	8(%esp), %edx
 	movl	%edx, (%eax)
 	movl	$0, 4(%eax)
-	ret
+	ret BYTES_TO_POP_ON_STRUCT_RETURN
 
 /* */
 /* $PchId: cvu64.ack.s,v 1.2 1996/04/11 18:59:57 philip Exp $ */

lib/libc/arch/i386/int64/make64.S

@@ -1,6 +1,8 @@
 /*	make64() - make a 64 bit number from two 32 bit halves */
 /*							Author: Kees J. Bot */
 /*								7 Dec 1995 */
+#include <minix/compiler.h>
+
 .text
 .globl	_make64
 
@@ -11,7 +13,7 @@ _make64:
 	movl	%edx, (%eax)
 	movl	12(%esp), %edx
 	movl	%edx, 4(%eax)
-	ret
+	ret BYTES_TO_POP_ON_STRUCT_RETURN
 
 /* */
 /* $PchId: make64.ack.s,v 1.2 1996/04/11 18:59:57 philip Exp $ */

lib/libc/arch/i386/int64/mul64u.S

@@ -1,6 +1,8 @@
 /*	mul64u() - unsigned long by unsigned multiply giving 64 bit result */
 /*							Author: Kees J. Bot */
 /*								7 Dec 1995 */
+#include <minix/compiler.h>
+
 .text
 .globl	_mul64u
 
@@ -12,7 +14,7 @@ _mul64u:
 	movl	%eax, (%ecx)
 	movl	%edx, 4(%ecx)
 	movl	%ecx, %eax
-	ret
+	ret BYTES_TO_POP_ON_STRUCT_RETURN
 
 /* */
 /* $PchId: mul64u.ack.s,v 1.2 1996/04/11 18:59:57 philip Exp $ */

lib/libc/arch/i386/int64/sub64.S

@@ -1,5 +1,7 @@
 /*	sub64() - 64 bit subtraction			Author: Kees J. Bot */
 /*								7 Dec 1995 */
+#include <minix/compiler.h>
+
 .text
 .globl	_sub64
 
@@ -12,7 +14,7 @@ _sub64:
 	movl	12(%esp), %edx
 	sbbl	20(%esp), %edx
 	movl	%edx, 4(%eax)
-	ret
+	ret BYTES_TO_POP_ON_STRUCT_RETURN
 
 /* */
 /* $PchId: sub64.ack.s,v 1.2 1996/04/11 18:59:57 philip Exp $ */

lib/libc/arch/i386/int64/sub64u.S

@@ -1,5 +1,7 @@
 /*	sub64() - unsigned from 64 bit subtraction	Author: Kees J. Bot */
 /*								7 Dec 1995 */
+#include <minix/compiler.h>
+
 .text
 .globl	_sub64u, _sub64ul
 
@@ -14,7 +16,7 @@ _sub64ul:
 	movl	12(%esp), %edx
 	sbbl	$0, %edx
 	movl	%edx, 4(%eax)
-	ret
+	ret BYTES_TO_POP_ON_STRUCT_RETURN
 
 /* */
 /* $PchId: sub64u.ack.s,v 1.2 1996/04/11 18:59:57 philip Exp $ */