Add UPDATING entries and bump version

Approved by:	so

UPDATING

@@ -16,6 +16,13 @@ from older versions of FreeBSD, try WITHOUT_CLANG and WITH_GCC to bootstrap to
 the tip of head, and then rebuild without this option. The bootstrap process
 from older version of current across the gcc/clang cutover is a bit fragile.
 
+20210629:	p19	FreeBSD-EN-21:19.libcasper
+			FreeBSD-EN-21:22.linux_futex
+
+		libcasper assertion failures [EN-21:19.libcasper]
+
+		Linux compatibility layer futex(2) system call vulnerability [EN-21:22.linux_futex]
+
 20210601:	p18	FreeBSD-EN-21:17.libradius
 
 		Incorrect validation in rad_get_attr(3) [FreeBSD-EN-21:17.libradius]

sys/conf/newvers.sh

@@ -46,7 +46,7 @@
 
 TYPE="FreeBSD"
 REVISION="12.1"
-BRANCH="RELEASE-p18"
+BRANCH="RELEASE-p19"
 if [ -n "${BRANCH_OVERRIDE}" ]; then
 	BRANCH=${BRANCH_OVERRIDE}
 fi