Add support for architecture ppc64le

[ddeka2910]

Include only php 7.1 and 7.2 for ppc64le.

[ddeka2910]

For more info tag @gerrith3

[gerrith3]

@clue always a tough question - sometimes I answer with: can you prove that it runs on ppc64le without change? (btw, easy answer is yes, when it is running in travis ;-). But usually the issue with a project like this is the dependencies in your composer.json - are you sure that all of those dependencies and versions are available on ppc64le, thus enabling your package to be fully functional. Now, the testing that my team is doing before filing these indicates that yes, currently your dependencies are all available for ppc64le. There may be some differences in which versions of php are available (Power transitioned its Linux offerings to little endian (same as Intel) in 2016 - so versions of php build before then typically don't run on modern ppc64le. The testing and recommendations we make provide clarity as to exactly what build/run combinations actually do work out of the box.

I hope that helps, at least a bit on the justification.

[cboden]

With #124 we're now using GitHub CI instead of Travis. Can this PR be updated to target GH's CI file instead?