fix name handling in `tar-gzip'
speed up gzip by moving struct definitions

Moving the `define-structs' to the module top level
makes it easier for the JIT and cuts compression time by
about 1/3.
file/gzip: misc clean-up

Separate state and functions, and convert a key loop to functional
style. As it turns out, this has no significant effect on performance,
but it looks a lot better to me.
optimizer: certain bitwise-operation patterns always produce fixnums
setup/getinfo: change bootstrap mode to try bytecode

Loading "info.rkt" files always from source turns out to be
expensive (adding 1 second or so on my machine to the startup
time for `raco setup'). Change bootstrap mode to try the compiled
form and fall back to source if its doesn't work.
Support non-GNU `make'