Various csi sequences contain intermediate characters between the
parameters and the final character. Introduce a additional state that
cleanly ignores these sequences.

This allows the vt to ignore these sequences used by more capable
terminal implementations such as "request mode", etc.
Signed-off-by: NMartin Hostettler <textshell@uchuujin.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>