Introduce nvim namespace: Move files.

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.

src/nvim/types.h

@@ -0,0 +1,19 @@
+/*
+ * VIM - Vi IMproved	by Bram Moolenaar
+ *
+ * Do ":help uganda"  in Vim to read copying and usage conditions.
+ * Do ":help credits" in Vim to see a list of people who contributed.
+ */
+
+#ifndef NEOVIM_TYPES_H
+#define NEOVIM_TYPES_H
+
+#include <stdint.h>
+
+/*
+ * Shorthand for unsigned variables. Many systems, but not all, have u_char
+ * already defined, so we use char_u to avoid trouble.
+ */
+typedef unsigned char char_u;
+
+#endif /* NEOVIM_TYPES_H */