Bump the static version string in version.mk.

We failed to do this before the 1.1 release, so that went out
still marked at 1.1 beta. The plan was to get rid of this file
but it's still used as a fallback by the msvc build.

version.mk

 # static version string; update manually every release.
-PACKAGE_VERSION = "1.1-beta"
+PACKAGE_VERSION = "1.1.x-git"