introduce library version plus git hash

This exposes the library version and git head hash it was built from
into LWS_LIBRARY_VERSION and LWS_BUILD_HASH.

These are combined into a version string that's both printed as a
notice log by the library and made available to the app using a new
api lws_get_library_version().  The version looks like

 1.1 178d78c

Signed-off-by: Andy Green <andy.green@linaro.org>
diff --git a/changelog b/changelog
index c865021..8e559c1 100644
--- a/changelog
+++ b/changelog
@@ -1,6 +1,17 @@
 Changelog
 ---------
 
+(development since 1.1....)
+
+User api additions
+------------------
+
+ - lws_get_library_version() returns a const char * with a string like
+ 	 "1.1 9e7f737", representing the library version from configure.ac
+	 and the git HEAD hash the library was built from
+
+
+
 v1.1-chrome26-firefox18
 =======================