Until now, creating the input_ctx was delayed until the command line
and config files were parsed. Separate creation and loading so that
input_ctx is available from start.
This should make it possible to simplify some things. For example,
some complications with Cocoa were apparently only because input_ctx
was available only "later". (Although I'm not sure if this is still
relevant, or if the Cocoa code should even be organized this way.)