Keep the stack aligned to a 16 byte boundary when calling init functions

so that we don't cause a bus error if they start storing SSE math stuff
on the stack.

MFC After: 1 week

lib/csu/i386-elf/crti.S

@@ -28,12 +28,14 @@
 	.globl	_init
 	.type	_init,@function
 _init:
+	sub	$12,%esp	/* re-align stack pointer */
 
 	.section .fini,"ax",@progbits
 	.align	4
 	.globl	_fini
 	.type	_fini,@function
 _fini:
+	sub	$12,%esp	/* re-align stack pointer */
 
 	.section .rodata
 .ascii "$FreeBSD$\0"

lib/csu/i386-elf/crtn.S

@@ -24,9 +24,11 @@
  */
 
 	.section .init,"ax",@progbits
+	add	$12,%esp
 	ret
 
 	.section .fini,"ax",@progbits
+	add	$12,%esp
 	ret
 
 	.section .rodata