documentation/poky-ref-manual: cleared up environment variable ambiguity

Some instances in the manual where it was not clear on whether
the subject was a shell environment variable or a BitBake
environment variable.  I cleared these up.

Reported-by: Robert P. J. Day <rpjday@crashcourse.ca>
(From yocto-docs rev: 123bb91a3954c98378cdd8bba0a35311eb53f37a)

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

documentation/poky-ref-manual/faq.xml

@@ -572,7 +572,7 @@
                  any network accesses to anything other than the PREMIRROR would fail.
              </para>
              <para>
-                 Poky also honors the standard environment variables 
+                 Poky also honors the standard shell environment variables 
                  <filename>http_proxy</filename>, <filename>ftp_proxy</filename>, 
                  <filename>https_proxy</filename>, and <filename>all_proxy</filename>
                  to redirect requests through proxy servers.

documentation/poky-ref-manual/ref-bitbake.xml

@@ -36,7 +36,7 @@
             The first thing BitBake does is look for the <filename>bitbake.conf</filename> file.
             The Yocto Project keeps this file in the Yocto Project file's <filename>meta/conf/</filename>
             directory.
-            BitBake finds it by examining the <filename>BBPATH</filename> environment 
+            BitBake finds it by examining its <filename>BBPATH</filename> environment 
             variable and looking for the <filename>meta/conf/</filename> 
             directory.
         </para>
@@ -54,7 +54,7 @@
             and the machine configuration file 
             (set by the 
             <filename><link linkend='var-MACHINE'>MACHINE</link></filename> variable).  
-            The <filename>DISTRO</filename> and <filename>MACHINE</filename> environment 
+            The <filename>DISTRO</filename> and <filename>MACHINE</filename> BitBake environment 
             variables are both usually set in 
             the <filename>local.conf</filename> file. 
             Valid distribution