ftpcmd.c: Cast variable instead, to handle both 32/64 bit.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
Makefile: Handle parallell building better, remove -Werror

The file defs.h must be built before potentially any other .o file
in uftpd (except libuev).

Remove -Werror, we shouldn't allow build errors, but keeping the
code warning free on all archs and support older distributions is
a non-trivial task for this little project.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>