Remove the need for backslashes in syscalls.master.

Join non-special lines together until we hit a line containing a '}'
character. This allows the function declaration body to be split
across multiple lines without backslash continuation characters.

Continue to join lines ending with backslashes to allow gradual
migration and to support out-of-tree syscall vectors

Reviewed by:	emaste, kib
Obtained from:	CheriBSD
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D17488

sys/kern/makesyscalls.sh

@@ -68,13 +68,33 @@ if [ -n "$2" ]; then
 fi
 
 sed -e '
-:join
+	# FreeBSD ID, includes, comments, and blank lines
+	/.*\$FreeBSD/b done_joining
+	/^[#;]/b done_joining
+	/^$/b done_joining
+
+	# Join lines ending in backslash
+:joining
 	/\\$/{a\
 
 	N
 	s/\\\n//
-	b join
+	b joining
 	}
+
+	# OBSOL, etc lines without function signatures
+	/^[0-9][^{]*$/b done_joining
+
+	# Join incomplete signatures.  The { must appear on the first line
+	# and the } must appear on the last line (modulo lines joined by
+	# backslashes).
+	/^[^}]*$/{a\
+
+	N
+	s/\n//
+	b joining
+	}
+:done_joining
 2,${
 	/^#/!s/\([{}()*,]\)/ \1 /g
 }