Flesh out the definition of __mac_execve(): per earlier discussion,

it's essentially execve() with an optional MAC label argument.

Approved by:	re
Obtained from:	TrustedBSD Project
Sponsored by:	DARPA, Network Associates Laboratories

sys/kern/syscalls.master

@@ -600,7 +600,8 @@
 			    void *data, size_t nbytes); }
 414	STD	BSD	{ int extattr_delete_link(const char *path, \
 			    int attrnamespace, const char *attrname); }
-415	UNIMPL	BSD	__mac_execve
+415	MSTD	BSD	{ int __mac_execve(char *fname, char **argv, \
+			    char **envv, struct mac *mac_p); }
 416	MSTD	POSIX	{ int sigaction(int sig, const struct sigaction *act, \
 			    struct sigaction *oact); }
 417	MSTD	BSD	{ int sigreturn(const struct __ucontext *sigcntxp); }