Document src.opts.mk changes and the decoupling of /etc/src.conf from

anything but the source tree.

Makefile.inc1

@@ -45,7 +45,7 @@
 .error "Both TARGET and TARGET_ARCH must be defined."
 .endif
 
-.include <src.opts.mk>
+.include "share/mk/src.opts.mk"
 .include <bsd.arch.inc.mk>
 .include <bsd.compiler.mk>
 

UPDATING

@@ -12,9 +12,9 @@ Items affecting the ports and packages system can be found in
 /usr/ports/UPDATING.  Please read that file before running portupgrade.
 
 NOTE: FreeBSD has switched from gcc to clang. If you have trouble bootstrapping
-from older versions of FreeBSD, try WITHOUT_CLANG to bootstrap to the tip of
-head, and then rebuild without this option. The bootstrap process from
-older version of current is a bit fragile.
+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 accorss the gcc/clang cutover is a bit fragile.
 
 NOTE TO PEOPLE WHO THINK THAT FreeBSD 11.x IS SLOW:
 	FreeBSD 11.x has many debugging features turned on, in both the kernel
@@ -31,6 +31,17 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 11.x IS SLOW:
 	disable the most expensive debugging functionality run
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20140505:
+	/etc/src.conf now affects only builds of the FreeBSD src tree. In the
+	past, it affected all builds that used the bsd.*.mk files. The old
+	behavior was a bug, but people may have relied upon it. To get this
+	behavior back, you can .include /etc/src.conf from /etc/make.conf
+	(which is still global and isn't changed). This also changes the
+	behavior of incremental builds inside the tree of individual
+	directories. Set MAKESYSPATH to ".../share/mk" to do that.
+	Although this has survived make universe and some upgrade scenarios,
+	other upgrade scenarios may have broken.
+
 20140430:
 	The lindev device has been removed since /dev/full has been made a
 	standard device.  __FreeBSD_version has been bumped.