remove __vfork alias

this was added so that posix_spawn and possibly other functionality
could be implemented in terms of vfork, but that turned out to be
unsafe. any such usage needs __clone with proper handling of stack
lifetime.

src/process/arm/vfork.s

@@ -1,9 +1,6 @@
 .syntax unified
-.global __vfork
-.weak vfork
-.type __vfork,%function
+.global vfork
 .type vfork,%function
-__vfork:
 vfork:
 	mov ip, r7
 	mov r7, 190

src/process/i386/vfork.s

@@ -1,8 +1,5 @@
-.global __vfork
-.weak vfork
-.type __vfork,@function
+.global vfork
 .type vfork,@function
-__vfork:
 vfork:
 	pop %edx
 	mov $190,%eax

src/process/s390x/vfork.s

@@ -1,8 +1,5 @@
-	.global __vfork
-	.weak vfork
-	.type __vfork,%function
+	.global vfork
 	.type vfork,%function
-__vfork:
 vfork:
 	svc 190
 	.hidden __syscall_ret

src/process/sh/vfork.s

@@ -1,8 +1,5 @@
-.global __vfork
-.weak vfork
-.type __vfork,@function
+.global vfork
 .type vfork,@function
-__vfork:
 vfork:
 	mov #95, r3
 	add r3, r3

src/process/vfork.c

@@ -2,9 +2,8 @@
 #include <unistd.h>
 #include <signal.h>
 #include "syscall.h"
-#include "libc.h"
 
-pid_t __vfork(void)
+pid_t vfork(void)
 {
 	/* vfork syscall cannot be made from C code */
 #ifdef SYS_fork
@@ -13,5 +12,3 @@ pid_t __vfork(void)
 	return syscall(SYS_clone, SIGCHLD, 0);
 #endif
 }
-
-weak_alias(__vfork, vfork);

src/process/x32/vfork.s

@@ -1,8 +1,5 @@
-.global __vfork
-.weak vfork
-.type __vfork,@function
+.global vfork
 .type vfork,@function
-__vfork:
 vfork:
 	pop %rdx
 	mov $0x4000003a,%eax /* SYS_vfork */

src/process/x86_64/vfork.s

@@ -1,8 +1,5 @@
-.global __vfork
-.weak vfork
-.type __vfork,@function
+.global vfork
 .type vfork,@function
-__vfork:
 vfork:
 	pop %rdx
 	mov $58,%eax