This fixes #1788. This also reverts #280. For #280, at the time, this
change to ignore versions was correct. Two years after #280, Debian
began allowing `Provides` field to have versions.
This change also fixes bug in gem-to-deb conversion where previously an
incorrect Provides syntax would be generated (but thanks to #280,
removed), so this bug was only noticed after #280 was undone!
Computers are hard sometimes.
Added tests for gem-to-deb conversion specifically for the Provides
field.
Tested manually with Docker on Ubuntu 14.04 and 18.04 and results meet
expectations.
The history here is follows:
* In 2012, fpm was patched to remove version specifiers in Provides
field because Debian didn't support it.
* In 2014, Debian dpkg[1] added support for versions in Provides field
* Somewhere between 2015-2018, Debian and Ubuntu included this new
version of dpkg.
* Debian packaging policy docs (v4.4.0) was updated to allow versions
in the Provides field.
Expected impacts:
* Older versions of dpkg/etc should _ignore_ the presence of a version
specifier. Testing on Ubuntu 14.04 confirmed this.
* Newer versions of dpkg/etc should respect the presence of a version
specifier. Testing on Ubuntu 18.04 confirmed this.
[1] https://launchpad.net/debian/+source/dpkg/1.17.11
