Enable MK_TESTS by default, take 2.

This is a redo of r267424, which was reverted in r267432 because it broke
"make buildworld" from FreeBSD 9.x.  This issue has been resolved and this
change is still "make tinderbox" clean.

share/mk/src.opts.mk

@@ -144,6 +144,7 @@ __DEFAULT_YES_OPTIONS = \
     SYSINSTALL \
     TCSH \
     TELNET \
+    TESTS \
     TEXTPROC \
     UNBOUND \
     USB \
@@ -169,7 +170,6 @@ __DEFAULT_NO_OPTIONS = \
     SHARED_TOOLCHAIN \
     SORT_THREADS \
     SVN \
-    TESTS \
     USB_GADGET_EXAMPLES
 
 #

tools/build/options/WITHOUT_TESTS

@@ -0,0 +1,9 @@
+.\" $FreeBSD$
+Set to not build nor install the
+.Fx
+Test Suite in
+.Pa /usr/tests/ .
+See
+.Xr tests 7
+for more details.
+This also disables the build of all test-related dependencies, including ATF.

tools/build/options/WITH_TESTS

@@ -1,8 +0,0 @@
-.\" $FreeBSD$
-Set to install the
-.Fx
-Test Suite in
-.Pa /usr/tests/ .
-See
-.Xr tests 7
-for more details.