[packages/rpm-specdump] - define rpm version from pkg-config - drop support for antiquated rpm

[Elan Ruusamäe]

On 10/19/20 1:24 AM, baggins wrote:

> +RPM_FORMAT_VERSION := `pkg-config --modversion rpm | cut -d . -f 1`
> +RPM_MAJOR_VERSION := `pkg-config --modversion rpm | cut -d . -f 1`
> +RPM_MINOR_VERSION := `pkg-config --modversion rpm | cut -d . -f 1`
>   

these three are all the same, or I'm not seeing something?