Add a cmOutputConverter to the cmLinkLineComputer and factory methods to
facilitate shell escapes.

Add state to the cmLinkLineComputer to record whether outputting for
response files or for watcom, to satisfy the cmOutputConverter API.
These are constant for the lifetime of the cmLinkLineComputer, even when
its functionality is extended in the future.  This also keeps the
signatures of cmLinkLineComputer relatively simple.

Pass the cmComputeLinkInformation as a method parameter so that
cmLinkLineComputer is free from target-specific state.  An instance
should be usable for all targets in a directory.