Bump pack version to post-release 5.1.1-dev0 for development.

ARM.CMSIS.pdsc

@@ -8,6 +8,9 @@
   <url>http://www.keil.com/pack/</url>
 
   <releases>
+    <release version="5.1.1-dev0">
+	  Active development...
+	</release>
     <release version="5.1.0" date="2017-08-04">
       CMSIS-Core(M): 5.0.2 (see revision history for details)
 	  - Changed Version Control macros to be core agnostic. 

README.md

@@ -1,6 +1,6 @@
 # CMSIS Version 5
 
-The branch *master* of this GitHub repository contains the CMSIS Version 5.0.1.  The [documentation](http://arm-software.github.io/CMSIS_5/General/html/index.html) is available under http://arm-software.github.io/CMSIS_5/General/html/index.html
+The branch *master* of this GitHub repository contains the CMSIS Version 5.1.0  The [documentation](http://arm-software.github.io/CMSIS_5/General/html/index.html) is available under http://arm-software.github.io/CMSIS_5/General/html/index.html
 
 Use [Issues](https://github.com/ARM-software/CMSIS_5#issues-and-labels) to provide feedback and report problems for CMSIS Version 5.