ref-manual: Updates to CMake and cmake.bbclass.

I cleaned up the terminology used for the CMake build system.
I provided some meaningful links to a good overview page for CMake.
I also built in some cross-referencing as needed.

(From yocto-docs rev: 7c38add39b97a7a8786a1be53f9ff549e4727fad)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/migration.xml

@@ -5557,8 +5557,9 @@ id=f4d4f99cfbc2396e49c1613a7d237b9e57f06f81'>commit message</ulink>.
                     incompatible with other implementations.
                     </para></listitem>
                 <listitem><para>
-                    By default, the <filename>cmake</filename> class uses
-                    <filename>ninja</filename> instead of
+                    By default, the
+                    <link linkend='ref-classes-cmake'><filename>cmake</filename></link>
+                    class uses <filename>ninja</filename> instead of
                     <filename>make</filename> for building.
                     This improves build performance.
                     If a recipe is broken with <filename>ninja</filename>, then

documentation/ref-manual/ref-classes.xml

@@ -449,12 +449,13 @@
     <title><filename>cmake.bbclass</filename></title>
 
     <para>
-        The <filename>cmake</filename> class allows for
-        recipes that need to build software using the CMake build system.
+        The <filename>cmake</filename> class allows for recipes that need to
+        build software using the
+        <ulink url='https://cmake.org/overview/'>CMake</ulink> build system.
         You can use the
         <link linkend='var-EXTRA_OECMAKE'><filename>EXTRA_OECMAKE</filename></link>
-        variable to specify additional configuration options to be passed on
-        the <filename>cmake</filename> command line.
+        variable to specify additional configuration options to be passed
+        using the <filename>cmake</filename> command line.
     </para>
 </section>
 

documentation/ref-manual/ref-variables.xml

@@ -4633,7 +4633,12 @@
             <glossdef>
                 <para role="glossdeffirst">
 <!--                <para role="glossdeffirst"><imagedata fileref="figures/define-generic.png" /> -->
-                    Additional <filename>cmake</filename> options.
+                    Additional
+                    <ulink url='https://cmake.org/overview/'>CMake</ulink>
+                    options.
+                    See the
+                    <link linkend='ref-classes-cmake'><filename>cmake</filename></link>
+                    class for additional information.
                 </para>
             </glossdef>
         </glossentry>