Added SAL annotatations to system calls.

Modify makesyscalls.sh to strip out SAL annotations.

No functional change.

This is based on work I started in CheriBSD and use to validate fat
pointers at the syscall boundary.  Tal Garfinkel reviewed the changes,
added annotations to COMPAT* syscalls and is using them in a record and
playback framework.  One can envision other uses such as a WITNESS-like
validator for copyin/out as speculated on in the review.

As this time we are only annotating sys/kern/syscalls.master as that is
sufficient for userspace work.  If kernel use cases materialize, we can
annotate other syscalls.master as needed.

Submitted by:	Tal Garfinkel <talg@cs.stanford.edu>
Sponsored by:	DARPA, AFRL (in part)
Differential Revision:	https://reviews.freebsd.org/D14285

sys/kern/makesyscalls.sh

@@ -400,6 +400,16 @@ sed -e '
 			}
 			if (argtype[argc] == "")
 				parserr($f, "argument definition")
+
+			# The parser adds space around parens.
+			# Remove it from annotations.
+			gsub(/ \( /, "(", argtype[argc]);
+			gsub(/ \)/, ")", argtype[argc]);
+
+			#remove annotations
+			gsub(/_In[^ ]*[_)] /, "", argtype[argc]);
+			gsub(/_Out[^ ]*[_)] /, "", argtype[argc]);
+
 			argname[argc]=$f;
 			f += 2;			# skip name, and any comma
 		}