prctl: fix system call wrapper

The argument names used in the prctl wrapper collide with the internal
variable names in syscall wrapper macros on some architecture. This
currently breaks xtensa. grep for '\b_a[0-9]' indicates that metag and
microblaze might also be affected.

Prefix argument names with '_prctl' to avoid collision.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

libc/sysdeps/linux/common/prctl.c

@@ -12,5 +12,6 @@
 
 #ifdef __NR_prctl
 int prctl (int, long, long, long, long);
-_syscall5(int, prctl, int, option, long, _a2, long, _a3, long, _a4, long, _a5)
+_syscall5(int, prctl, int, option, long, _prctl_a2, long, _prctl_a3,
+		long, _prctl_a4, long, _prctl_a5)
 #endif