Fix a typo, unkown -> unknown
Handle -dumpversion in the same way as --version

This is called when wrapping gas-preprocessor around a normal
linux gcc.
Support converting arm assembly to armasm syntax

This syntax is supported by the official arm tools and
by Microsoft's assembler.

This currently only supports microsoft's assembler, the
armasm assembler in RVCT requires a few more tweaks to
be able to build libav.

The preprocessing is done by invoking cpp (do we need to
be able to override this?).

The converted output is written to a file instead of using
a pipe, since Microsoft's armasm can't read the input from
a pipe.
Do simple keyword replacements, commenting out and translation at the end

This allows the main part of the preprocessor to work with source
in the actual input format and not have to look for directives
in their translated form (which can be different depending on the
target).