file: speed up loading non-gzipped modules when zlib is enabled.
file: speed up loading non-gzipped modules when zlib is enabled.

Just now realized that my distro (Gentoo) enables support for gzip but
does not compress modules by default.

In this case it's better to have a special case that uses mmap()
instead of a loop of realloc() + gzread().

lucasdemarchi/kmod,lucasdemarchi/kmod,Distrotech/kmod,lpereira/kmod,Distrotech/kmod,Distrotech/kmod,pmmccorm/kmod,lpereira/kmod,pmmccorm/kmod,pmmccorm/kmod,lucasdemarchi/kmod,lpereira/kmod