Medium: build: add compatibility wrappers for conditional builds in legacy RPM versions

Legacy versions of RPM, most notably the one bundled with RHEL 4, do
not support conditional builds with the --with and --without
options. Add compatibility wrappers that define the necessary macros
in case they aren't yet natively defined yet.

("Stolen" from the spec file that DRBD uses.)

Mercurial revision: 0a0fd60527972563530320bc9691a9c16fb3229d