Updated patch for multiple users of readline event hook

[John W. Eaton]

On 17-Sep-2007, John Swensen wrote:

| Because the oct-rl-edit.c and oct-rl-hist.c were being compiled as C 
| file, rather than C++ files, I have attached 2 patches.  One is for 
| existing files and the other contains the new C++ versions of those two 
| files.

Those files are intended to be in C, so there should be no need to
convert them to C++.  They exist to provide C++ callable wrappers for
the C functions in libreadline.  Maybe this is not necessary now, but
it used to be needed because of the way some declarations were
writtten for readline (primarily function pointers, I think).

jwe