Document the sys/boot -> stand move in hier.7 and the top-level README.

Reviewed by:	imp
Differential Revision:	https://reviews.freebsd.org/D13353

README

@@ -66,6 +66,8 @@ secure		Cryptographic libraries and commands.
 
 share		Shared resources.
 
+stand		Boot loader sources.
+
 sys		Kernel sources.
 
 tests		Regression tests which can be run by Kyua.  See tests/README

README.md

@@ -68,6 +68,8 @@ secure			Cryptographic libraries and commands.
 
 share			Shared resources.
 
+stand			Boot loader sources.
+
 sys				Kernel sources.
 
 tests			Regression tests which can be run by Kyua.  See tests/README

share/man/man7/hier.7

@@ -28,7 +28,7 @@
 .\"	@(#)hier.7	8.1 (Berkeley) 6/5/93
 .\" $FreeBSD$
 .\"
-.Dd November 16, 2017
+.Dd December 3, 2017
 .Dt HIER 7
 .Os
 .Sh NAME
@@ -644,6 +644,8 @@ build directory for files in
 .It Pa share/
 source for files in
 .Pa /usr/share
+.It Pa stand/
+boot loader source code
 .It Pa sys/
 kernel source code
 .Bl -tag -width "opencrypto/" -compact