documentation: Updated Manual revision tables with "April 2015"

(From yocto-docs rev: a012e34956b8ac2fa7610e264f460bc27bdd66d8)

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

documentation/adt-manual/adt-manual.xml

@@ -83,7 +83,7 @@
             </revision>
             <revision>
                 <revnumber>1.8</revnumber>
-                <date>Sometime in 2015</date>
+                <date>April 2015</date>
                 <revremark>Released with the Yocto Project 1.8 Release.</revremark>
             </revision>
        </revhistory>

documentation/bsp-guide/bsp-guide.xml

@@ -95,7 +95,7 @@
             </revision>
             <revision>
                 <revnumber>1.8</revnumber>
-                <date>Sometime in 2015</date>
+                <date>April 2015</date>
                 <revremark>Released with the Yocto Project 1.8 Release.</revremark>
             </revision>
         </revhistory>

documentation/dev-manual/dev-manual.xml

@@ -73,7 +73,7 @@
             </revision>
             <revision>
                 <revnumber>1.8</revnumber>
-                <date>Sometime in 2015</date>
+                <date>April 2015</date>
                 <revremark>Released with the Yocto Project 1.8 Release.</revremark>
             </revision>
         </revhistory>

documentation/kernel-dev/kernel-dev.xml

@@ -58,7 +58,7 @@
             </revision>
             <revision>
                 <revnumber>1.8</revnumber>
-                <date>Sometime in 2015</date>
+                <date>April 2015</date>
                 <revremark>Released with the Yocto Project 1.8 Release.</revremark>
             </revision>
         </revhistory>

documentation/mega-manual/mega-manual.xml

@@ -42,7 +42,7 @@
         <revhistory>
             <revision>
                 <revnumber>1.8</revnumber>
-                <date>Sometime in 2015</date>
+                <date>April 2015</date>
                 <revremark>Released with the Yocto Project 1.8 Release.</revremark>
             </revision>
        </revhistory>

documentation/profile-manual/profile-manual.xml

@@ -58,7 +58,7 @@
             </revision>
             <revision>
                 <revnumber>1.8</revnumber>
-                <date>Sometime in 2015</date>
+                <date>April 2015</date>
                 <revremark>Released with the Yocto Project 1.8 Release.</revremark>
             </revision>
         </revhistory>

documentation/ref-manual/ref-manual.xml

@@ -89,7 +89,7 @@
             </revision>
             <revision>
                 <revnumber>1.8</revnumber>
-                <date>Sometime in 2015</date>
+                <date>April 2015</date>
                 <revremark>Released with the Yocto Project 1.8 Release.</revremark>
             </revision>
         </revhistory>