Removed tgi_load() and all corresponding infrastructure. The idea behind tgi_load...

Removed tgi_load() and all corresponding infrastructure. The idea behind tgi_load() was to be able to describe a TGI mode in a target-neutral way by resolution and colordepth. However it turned out that there arn't any cc65 targets sharing any resolution. As a result the only working target-independent approach for a TGI program is to call tgi_loaddriver(tgi_stddrv); and then look up the resolution provided - and to adapt to that resolution.

git-svn-id: svn://svn.cc65.org/cc65/trunk@5021 b7a2c559-68d2-44c3-8de9-860c34a00d81