Extend version number and README to indicate this Kitware feature branch

Pending upstream integration of the features added by this branch,
extend the version number of Ninja to indicate that it has the
'jobserver' feature so that tools can detect availability.

README.md

@@ -1,3 +1,25 @@
+Kitware maintains this branch of Ninja in order to provide features
+that have not yet been integrated upstream:
+
+* make-style jobserver support
+
+This branch may be *rebased* without notice for maintenance on top of
+the upstream `master` branch.  It will be removed once upstream has
+integrated the features.
+
+Parts of this branch are under upstream consideration:
+
+* https://github.com/ninja-build/ninja/pull/1140
+
+As each PR is accepted additional parts of this branch will be submitted
+incrementally.
+
+Binaries built from versions of this branch are available here:
+
+* https://github.com/Kitware/ninja/releases
+
+-----------------------------------------------------------------------------
+
 # Ninja
 
 Ninja is a small build system with a focus on speed.

src/version.cc

@@ -18,7 +18,7 @@
 
 #include "util.h"
 
-const char* kNinjaVersion = "1.10.0.git";
+const char* kNinjaVersion = "1.10.0.git.kitware.jobserver-1";
 
 void ParseVersion(const string& version, int* major, int* minor) {
   size_t end = version.find('.');