Fix bug in GetHandleCharp.

No handles are ever registered with TYPE_{CHAR,INT8,UINT8}_P, only
TYPE_VOID_P.
Fix bugs in generated functions that return void.
WIP on libgit2 example
Use pepper_canary instead of pepper_35.

This gets a working implementation of realpath.
Add more to the git example.

It fails when trying to create the signature. I also added giterr_last
to extract the most recent error.
Fix the git example after removing DestroyCommand.

Also, use implicit string->char* conversion.
Nicer phony targets for examples.
Cleanup .gitignore
Add dependency on <filename>.json to build.ninja
Assert to catch missing context in function call
Finish git init example