input/logicport: introduce input module for LogicPort File (*.lpf)

input/logicport: introduce input module for LogicPort File (*.lpf)

Implement an input module for .lpf files, the "LogicPort File" format of
the Intronix LA1034 vendor software. This version supports wires with
enabled and inverted state, compressed samples, signal names, signal
groups (but not multiple assignment), and automatic format detection.

The logic which determines whether "the file header" was completely
received, and sample data can get sent to the session, implements an
assumption in the absence of a better and more reliable condition.

Invalid input gets rejected, but diagnostics is rather limited. Since
all channels get to be the member of a channel group, either specified
by the user in the input file, or arranged for in the input module, the
"missing separator" part of bug 1186 has become obsolete.