Fix references to ISA 2.7, which should be 2.07

Fixes #93.

Signed-off-by: Bill Schmidt <wschmidt@linux.ibm.com>

specification/ch_1.xml

@@ -66,7 +66,7 @@
     <itemizedlist>
       <listitem>
         <para>
-        <emphasis>Power Instruction Set Architecture,</emphasis> Versions 2.7
+        <emphasis>Power Instruction Set Architecture,</emphasis> Versions 2.07
 	and 3.0, IBM, 2013-2016. 
         <emphasis>
           <link xl:href="http://www.power.org">http://www.power.org

specification/ch_2.xml

@@ -20,7 +20,7 @@ xml:id="dbdoclet.50655240_pgfId-1156194">
     64-bit features to implement the ELF ABI version 2.</para>
     <section xml:id="dbdoclet.50655240___RefHeading___Toc377640572">
       <title>Processor Architecture</title>
-      <para>This ABI is predicated on, at a minimum, Power ISA version 2.7 and
+      <para>This ABI is predicated on, at a minimum, Power ISA version 2.07 and
       contains additional implementation characteristics.</para>
       <para>All OpenPOWER instructions that are defined by the Power
       Architecture can be assumed to be implemented and to work as specified.