rust-packaging >= 26 now has "official" support for overriding the
installation of library sources / binary targets by setting RPM macros.
This commit adds settings to correspond to the %cargo_install_lib and
%cargo_install_bin macros and plugs them through to the spec generator.
References to the the private %__cargo_is_bin and %__cargo_is_lib macros,
which could previously be used to hack this behaviour, were removed.
Remove documentation for rust2rpm.conf file format from the README. The
custom INI-based format is deprecated in favor of rust2rpm.toml. Both
formats are documented, including a migration guide from the old to the
new format.
The included build script shows how to build man pages from the asciidoc
source files.
