config.mak: rename strict_compilation to strict

This is much less annoying to type when I want to override
it.
config.mak: stop using ccache

There is an annoying bug in gcc 4.8 and 4.9 which causes a
split compilation (as used by ccache) to fail to report
warnings!
config.mak: compile without gettext

I don't always have this installed, and I don't use the i18n
anyway.
config.mak: compile without tcl/tk

I don't usually have tcl installed these days, and this
simplifies the compilation a little.