loadtools/scripts: gtm900.config renamed to gen4.config It turns out that a GTM900 variant exists with 8 MiB flash, thus -h gen8 needs to be used for GTM900 modules as the general case, and the old -h gtm900 config is best renamed to -h gen4, although not currently official for any actual target.

This host side library contains common modules for tools like fc-tmsh and
g23sh which operate asynchronously.  This code has been factored out of
fc-tmsh.