3 small patches to please Debian package maintainers

Hi,
the following patches do 3 things:
    1) fixes spelling errors (really minor patch)
    2) updates makefiles to respect outer environmenet variables like $LIBDIR, $CFLAGS, $CPPFLAGS, and $LDFLAGS
    3) allows to build hwinfo outside github clone; if HWINFO_VERSION is defined then it is used to provide version number instead of git2log which has to be run inside git repository; also both "VERSION" and "changelog" are added to cleaned files

Cheers,
Tomasz