patches to build on freebsd 12

- added cc and ar scripts for freebsd12.amd64
- fix for sfio macro SF_FLAGS also being defined for sendfile(2) in socket.h
-- fix is to hide the sendfile(2) macro
- defined _STDFILE_DECLARED to handle FILE macro incompatibility
- added test in std/features/procfs to deal with freebsd kvm interface
-- being different from what AST expects (for ps.c)
- fix for std/banner.c to clean up main() definition
- changed comment in ar.* scripts to match cc.* scripts

src/cmd/INIT/ar.freebsd12.amd64

@@ -0,0 +1,6 @@
+: linux.i386-64 ar wrapper
+
+case $1 in
+*x*) /usr/bin/ar "$@" ;;
+*)   /usr/bin/ar U"$@" ;;
+esac

src/cmd/INIT/ar.linux.i386-64

@@ -1,4 +1,4 @@
-: stupid stupid stupid to require a non-standard option for ar to work : 2009-10-06 :
+: linux.i386-64 ar wrapper
 
 case $1 in
 *x*) /usr/bin/ar "$@" ;;

src/cmd/INIT/cc.freebsd12.amd64

@@ -0,0 +1,9 @@
+: linux.i386-64 cc wrapper : 2006-02-14 :
+
+HOSTTYPE=freebsd12.amd64
+
+case " $* " in
+*" -dumpmachine "*) echo $HOSTTYPE; exit ;;
+esac
+
+/usr/bin/cc -P "$@"