ref-manual: Updates to clarify Fetcher URL directory parameters

Updated the SRC_URI variable description to cross-reference
the "Fetchers" section in the BitBake User Manual and added
some more Fetcher URL parameters specific to certain fetchers.
This was done to help clarify how to put fetched code into
specific directories.

Also updated the bin_packages.bbclass description to have a
better example.  Used a git:// fetcher example and provided

some specific URL parameters.

(From yocto-docs rev: 7133b49092096c253ffce99f39d4fa6db7810061)

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

documentation/ref-manual/ref-classes.xml

@@ -211,14 +211,22 @@
         use for this class.
         <note>
             For RPMs and other packages that do not contain a subdirectory,
-            you should specify a "subdir" parameter.
+            you should specify an appropriate fetcher parameter to point to
+            the subdirectory.
+            For example, if BitBake is using the Git fetcher
+            (<filename>git://</filename>), the "subpath" parameter limits
+            the checkout to a specific subpath of the tree.
             Here is an example where <filename>${BP}</filename> is used so that
             the files are extracted into the subdirectory expected by the
             default value of
             <link linkend='var-S'><filename>S</filename></link>:
             <literallayout class='monospaced'>
-     SRC_URI = "http://example.com/downloads/somepackage.rpm;subdir=${BP}"
+     SRC_URI = "git://example.com/downloads/somepackage.rpm;subpath=${BP}"
             </literallayout>
+            See the
+            "<ulink url='&YOCTO_DOCS_BB_URL;#bb-fetchers'>Fetchers</ulink>"
+            section in the BitBake User Manual for more information on
+            supported BitBake Fetchers.
         </note>
     </para>
 </section>