Split management of critcl's global options into package "critcl::gopt", and updated callers. Reworked "critcl::at" to use "gopt" instead of having its own option.
Switched fully to "ccconfig::get", dropping both "getconfigvalue", and direct access to c::xx variables.
Cleaned up the internal state of "critcl::ccconfig". Switched to nested dict for "toolchain", now "tools". Removed use of "v" namespace. Removed use of "c" namespace. Now dictionary "current". Eliminates need for "cofigvars" too.