Fixing linux builds

 
Hi all,
the branch https://github.com/OpenSmalltalk/opensmalltalk-vm/tree/fix_include_order
tries to fix the linux builds.
Eliot, could you review if compatible with TERF VM build?

I succeeded in building the linux and macos VM.
Travis status is still red, because there are random failures on macos
32bits spur during tests.
Either the tests result in SEGV or they stale...
Of course, when running all 5.1 tests with self compiled 32 bits VM, I
could not reproduce...