Enable actual build tests in Travis / OSX

[ianfixes]

Travis is running a null test right now as proof of concept for OSX. Replace with a build test

Build Matrix

macOS 64-bit JIT
Linux 32-bit JIT
MinGW 32-bit ---

How To Build

These builds need to be installed SDL2 framework/library.

macOS

1. Open SheepShaver/src/MacOSX/SheepShaver_Xcode8.xcodeproj
2. Set Build Configuration to Release
3. Build

Linux(x86)

$ cd macemu/SheepShaver
$ make links
$ cd src/Unix
$ ./autogen.sh
$ make

also:
https://www.emaculation.com/doku.php/compiling_sheepshaver_basilisk