Declare syscall parsers using SYS_FUNC macro

Introduce SYS_FUNC macro to declare and define all syscall parsers.

* Makefile.am (BUILT_SOURCES, CLEANFILES): Add sys_func.h.
(sys_func.h): New rule.
* defs.h (SYS_FUNC_NAME, SYS_FUNC): New macros.
* linux/syscall.h: Include "sys_func.h".
[NEED_UID16_PARSERS]: Use SYS_FUNC to declare uid16 syscall parsers.
Remove other declarations.
* linux/alpha/syscallent.h (160, 161): Add sys_ prefix to osf_statfs
and osf_fstatfs syscall parsers.
* *.c: Use SYS_FUNC to define syscall parsers.
diff --git a/prctl.c b/prctl.c
index 0ec0fc8..4a6bd25 100644
--- a/prctl.c
+++ b/prctl.c
@@ -281,8 +281,7 @@
 	return 0;
 }
 
-int
-sys_prctl(struct tcb *tcp)
+SYS_FUNC(prctl)
 {
 	return entering(tcp) ? prctl_enter(tcp) : prctl_exit(tcp);
 }
@@ -291,8 +290,7 @@
 # include <asm/prctl.h>
 # include "xlat/archvals.h"
 
-int
-sys_arch_prctl(struct tcb *tcp)
+SYS_FUNC(arch_prctl)
 {
 	if (entering(tcp))
 		printxval(archvals, tcp->u_arg[0], "ARCH_???");