This module will be used to implement remote management of objects through the
API. Object types to be registered must have a `uint64_t` field named 'handle'.
The map_* declarations and definitions are now created by a macro invocation
with a key type parameter. Also refactored server module to use the updated
version.
- Move `Map` structure definition to `map_defs.h`
- Use `KHASH_DECLARE` on map_defs.h to declare khash function prototypes.
- Redefine `map_foreach` into a macro
- Refactor server.c module to use the new `map_foreach` macro.
Move files from src/ to src/nvim/.
- src/nvim/ becomes the new root dir for nvim executable sources.
- src/libnvim/ is planned to become root dir of the neovim library.