Add hlc stack trace to Linux/Mac

[yuxiaomao]

Following #632 , I tried some implementation for hlc stack trace on Linux/MacOS using <execinfo.h>.

I did not use libunwind, as it does not seems to be adapted to the current structure: uwn_backtrace does not have more collaboration with other functions; resolve symbol of a single address would require to iterate though the stack.

I made a simple test with main() calling SimpleTest.hx, try catch and display the stack.

On Linux (gcc parameter -rdynamic is necessary to resolve function name):

Called from module ./bin/c/hlout/a.out(haxe_Exception_thrown+0x13d) [0x55f5d42fa5ed]
Called from module ./bin/c/hlout/a.out(SimpleTest_runThrowTest+0x617) [0x55f5d43024e7]
Called from module ./bin/c/hlout/a.out(fun$init+0x2156) [0x55f5d4306236]

On Mac:

Called from module 0   a.out                               0x0000000102f6aeb9 hlc_capture_stack + 9
Called from module 0   libhl.dylib                         0x000000010b639c07 hl_throw + 151
Called from module 0   a.out                               0x0000000102f76635 SimpleTest_runThrowTest + 661
Called from module 0   a.out                               0x0000000102f7c87f fun$init + 2447