Try makefile on travis ci

[weslleyspereira]

Add tests for the Makefile build system using make.inc.example on Travis CI. Tests performed on both Linux and Mac OS

[langou]

Thanks @weslleyspereira. That's a really good idea.

[codecov]

Codecov Report

Merging #500 (d0deb4b) into master (8bc7b0a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #500   +/-   ##
=======================================
  Coverage   83.33%   83.33%           
=======================================
  Files        1820     1820           
  Lines      170857   170857           
=======================================
  Hits       142384   142384           
  Misses      28473    28473           

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[weslleyspereira]

This PR should be ready for review. It mitigates the inconsistencies between the Makefile and CMake build systems reported in #488.

In this PR we have:

1. Travis CI working for both CMake and Makefile default configurations.
2. Compatible compilation flags in these two builds systems.

This PR does not modify the Meson build system.

[langou]

I think we are ready to retire the Meson build system. Thumbs up to this post if you think we should retire the Meson build system. Thumbs down if you think we should keep the Meson build system.