RFC: purify makefile

TL/DR: https://gist.github.com/wchristian/0758663fdc6fb3038d00

The .diff file in that patch displays the changes between the Makefile currently generated by EUMM, and the one generated by the EUMM of this branch. Please comment.

Long explanation:

Currently there is way too much perl code and other quote-requiring content in the Makefile generated by EUMM. This branch is a proof of concept towards changes that make it so shell-quoting is not a concern anymore, by putting all quotables in a Makefile.pm generated side-by-side with Makefile, and restricting instructions in Makefile to such that match `/[ 0-9a-z_-.]/i`.

There are still many changes needed, as i made this branch with a focus of getting it done quickly. It is meant to illustrate the idea with a working implementation to get feedback before refining it.