libgit2 v0.19.0 "gut merge"

Minor point release! We got a lot of rather large features that we
wanted to get settled in:

- New (threadsafe) cache for objects
- Iterator for Status
- New Merge APIs
- SSH support on *NIX
- Function context on diff
- Namespaces support
- Index add/update/remove with wildcard support
- Iterator for References
- Fetch and push refspecs for Remotes
- Rename support in Status
- New 'sys/` namespace for external headers with low-level APIs

As always, this comes with hundreds of bug fixes and performance
improvements. We're faster and better than ever. And we haven't broken
many APIs this time!

Build stuff.

include/git2/version.h

@@ -7,9 +7,9 @@
 #ifndef INCLUDE_git_version_h__
 #define INCLUDE_git_version_h__
 
-#define LIBGIT2_VERSION "0.18.0"
+#define LIBGIT2_VERSION "0.19.0"
 #define LIBGIT2_VER_MAJOR 0
-#define LIBGIT2_VER_MINOR 18
+#define LIBGIT2_VER_MINOR 19
 #define LIBGIT2_VER_REVISION 0
 
 #endif