Compile-time option for command key behaving as toggler

[TCH68k]

I like this small terminal multiplexer, for how small it is and also that it does not need any kind of terrible build systems (cmake, meson, etc.) and dependencies to build.

However, i found the way of giving commands to it a bit inconvenient. For instance, if i have four columns and i'd like to go to the last from the first, that will require to jump forth and back between G and the right cursor three times (and also the pressing and releaseing of Ctrl the same times). To set up a layout with multiple columns and rows will need even more jumping. Even if one will not make a mistake during the jumping around, it still doubles the required time to do it.

I understand that this multiplexer excels on simplicity - both in code and usage - and tries to avoid feature-creep, but since it also uses compile-time options for configuring the way it will work, i think a single compile-time option to make the command key behaving as a toggler, rather than a single-shot enabler could be useful and still will not put an unneeded feature into the binary.

Here is the patch: http://oscomp.hu/depot/mtm.c.patch
It is just nine more lines and the resulting binary does not differ in size, if the macro TOGGLING_COMMAND_KEY is defined.