implement --with-local-libedit

Add --with-local-libedit=(yes|auto|no) to control which libedit
implementation to use:
- yes - force local implementation
- auto - try system library, fallback to local implementation. Default
- no - force system library and fail if not found

Define NO_EDITCOMPLETE as AH_TEMPLATE() instead of adding to CFLAGS.

(lukem)