Garrett Cooper: If you are still around, you might want to review the following three changes in this new patch. I suspect they were mistakes in your version, but I cannot be 100 percent sure.

* Restoring length - 1 subtraction in call_readline() at line 1239
* Change #if __APPLE__ back to #ifdef
* Gnu Readline requires <stdio.h> to be included first, so I fixed the configure.ac script

Other changes in this new patch:

* Merged with current code
* Remove outdated comment about using a runtime library check
* Couple minor corrections to comments, conditional variable declarations, etc
* Fixed wrong HIST_ENTRY pointer type used in a Gnu Readline conditional branch
* Changed double single quote sign back to single single quote. I am no Autocrap expert, but it screwed up the generated comment in pyconfig.h.in.
* Add ability to include with <editline/readline.h>

Tested on Arch Linux with both Gnu Readline 6.3.008 and Editline 20150325-3.1 available:

No readline argument: Uses Gnu Readline
--with-readline=editline: Uses Editline
--with-readline=readline: Gnu Readline
--with-readline=yes: Gnu Readline
--with-readline: Gnu Readline
--with-readline=no: No “readline” module
--without-readline: No “readline” module
--without-readline=no: error: invalid package name: readline=no

However after successfully compiling with Editline, there are a couple bugs with keystrokes or output not being synchronized. I do not think I will spent much more effort on it. But perhaps other people are interested in taking this further.