serialization wip.  DOES NOT BUILD.  about 1/3 ported from parrot-ese to moar-isms...
s/MVMString/string/ as requested by https://github.com/MoarVM/MoarVM/commit/c46bed7181#commitcomment-3936131
Fix boring stuff in 6model/serialization.c
Implement MVM_sc_push_stable()
Remove stables_list from MVMSerializationWriter and fix one of its uses
Re-introduce stables_list to MVMSerializationWriter and use it
Minor fixes to 6model/serialization.c
Merge remote-tracking branch 'origin/master' into serialize
Pass flags for compiling shareable objects down to APR
Add . to library search path
Make void MVM_interp_enable_tracing() public
Add some make targets - in particular 'help'
Add 'sandwich' make target
Set cygwin shell to posix
Generate .dylib on MacOS
nuke trailing whitespace
lil bit of progress
li'l' bit more progress
Don't link 3rdparty libs twice when doing a shared build
Some fixes to string ops to make t/nqp/59-nqpop.t pass

Note that NQP/Parrot, NQP/JVM and NQP/MoarVM all
disagree on how nqp::substr() should behave.