kernel-dev: Rough text in for new chapter. Makefile edited.

The raw text for the second chapter is in by section.  This has
no formatting whatsoever.  I also edited the Makefile so that
the new "Common Tasks" chapter would make as part of the manual.

(From yocto-docs rev: 68bcc1e977fbdd7b1a4b448171d1149edc72db51)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/kernel-dev/kernel-dev.xml

@@ -59,9 +59,9 @@
 
     <xi:include href="kernel-dev-intro.xml"/>
 
-<!--
     <xi:include href="kernel-dev-common.xml"/>
 
+<!--
     <xi:include href="kernel-dev-advanced.xml"/>
 
     <xi:include href="kernel-dev-examples.xml"/>