Allow multiple uiomux_open() calls
Allow multiple uiomux_open() calls

Avoid unmapping the shared state, to allow multiple mappings to
exist (ie. multiple calls to uiomux_open() within the same process).
uiomux_close() is only called from uiomux_on_exit(), and the
shared state will be unmapped on exit anyway.

kfish/libuiomux,kfish/libuiomux