Update embedded Ruby to 2.5.3

[syndbg]

• Updates embedded Ruby to 2.5.3 - this is very important. Currently native extension-dependent plugins such as vagrant-libvirt don't work at all. "vagrant plugin install vagrant-libvirt" on Ubuntu 14.04 must display a user-friendly message if libvirt is not installed vagrant#7039 (comment) , https://gist.github.com/alexellis/046fa757113105ac1871644620756aed and many more
• Fix minor packages/differences and warnings

@chrisroberts

TODO:

• Verify that Ruby 2.4.0 is completely removed. Looks good to me, though.

What's been tested:

• Built a package and installed at Ubuntu 18.04 bionic
• Ran vagrant plugin install vagrant-libvirt - worked. Previously required manual CFLAGS to just make it install (but still not work) as mentioned in "vagrant plugin install vagrant-libvirt" on Ubuntu 14.04 must display a user-friendly message if libvirt is not installed vagrant#7039 (comment)
• Actually managed to use the libvirt provisioner via test-kitchen vagrant driver with provider: libvirt

[chrisroberts]

Hi there,

Thank you for this PR, however it is missing updates for the Ruby version provided in the Windows packaging as well as the appimage package. We are also not yet ready to upgrade the Ruby version to the 2.5 series.

I did test the vagrant-libvirt plugin on ubuntu 18.04 and found that the appimage version did have problems properly locating and building the plugin extensions. However, using the deb package for install worked as expected. I will investigate why the appimage version is failing and get that fixed up in the next release.

Cheers!