Bump version to 0.12.0

Bump version from 0.11.99 to 0.12.0 so that we don't forget to do this
when rc1 is released.

doc/Doxyfile

@@ -34,7 +34,7 @@ PROJECT_NAME           = Bitcoin
 # This could be handy for archiving the generated documentation or 
 # if some version control system is used.
 
-PROJECT_NUMBER         = 0.11.99
+PROJECT_NUMBER         = 0.12.0
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description 
 # for a project that appears at the top of each page and should give viewer 

doc/README.md

@@ -1,4 +1,4 @@
-Bitcoin Core 0.11.99
+Bitcoin Core 0.12.0
 =====================
 
 Setup

doc/README_windows.txt

@@ -1,4 +1,4 @@
-Bitcoin Core 0.11.99
+Bitcoin Core 0.12.0
 =====================
 
 Intro