add KEYMAP_ENTRY structure and typedef for Keymaps!

* finally found it in readline.h, not documented, must be so common
in GNU that they think every know about it!
* move callback functions to the top
* move structure definitions to top, after new types and callbacks
* add references to gnu readline git repository on savannah and
link to ctypes
* correct rl_insert function argtypes and restype
* add rl_complete, rl_initialize and rl_get_keymap_by_name
* some notes about keymap "names", which is an array of nicknames
* remove some dangline semicolons
* finish of setup readline