Enable 5.2 compatibility in Lua 5.3

[ccarrasc]

Is your feature request related to a problem? Please describe.
Lua 5.3 has a compiler flag set to allow 5.2 compatitibilty. I dug through the documentation and was unable to determine if excluding the flag was intentional or not.

Currently, attempting to execute the following results in an exception (attempt to call a nil value (field 'pow')):

         try (var lua = new Lua53()) {
             lua.openLibraries();
             var res = lua.eval("return math.pow(2, 2)");
             return res[0].toNumber();
         }

Describe the solution you'd like
Enable LUA_COMPAT_5_2 for lua53.

Additional context
I think all that is needed is to add -DLUA_COMPAT_5_2 to cFlags in lua53's build.gradle. I can open a PR, but it would take me some time to figure out how to build and test the change.

[ccarrasc]

I see the build failed when merged. I can't find the stacktrace to understand the issue. I assume that it's a CI issue since the build passed prior to merge, and there is nothing on top of it. If you need help debugging the build, let me know, @gudzpoz

[gudzpoz]

@ccarrasc For the CI errors, I have rather grown accustomed to them:

• Some of them just come up regularly during the ReactiveCircus/android-emulator-runner step when Google makes any changes to Android images/SDK and deleting the build cache usually fixes that.
• ReactiveCircus/android-emulator-runner also has a bunch of issues that seem to be triggered a bit randomly.
• Sometimes, jnigen will report failing to make dirs, which I really have no idea about (as the source code line is guarded by a !libsDir.exists() clause). But rerunning the step usually fixes that.

I consider most of these upstream issues, but have failed to make them reproducible enough to report them. You may look into them, but personally I won't recommend it since debugging CI-only issues is a pain (for me, at least).
Anyways, thank you again!