add an early form of the CompUnitRepo implementation

This is something to play with, and I expect that about
80% of this will land in nom. JVM backend and windows
support deserves more love than it got.
create libraries.cfg if missing
Merge branch 'nom' of github.com:rakudo/rakudo into eleven
build CompUnitRepo on moarv/jvm too
Merge branch 'nom' of github.com:rakudo/rakudo into eleven
fix for flat $/.ast

See https://github.com/moritz/json/commit/601d2a3b13e2f0dbe61a3083b77c69d708c6f133
handle .jar and .moarvm file extensions
add -m wrapper too
consider .jvm/.moarvm candidates besides .pir
choose names that do not hide JSON::Tiny
Move non-JVM-specific conc code out of src/vm/jvm.

This makes it clearer what bits are JVM-specific and need abstracting
or porting.
Re-work Thread class using new nqp::ops.
Move Thread.pm to src/core, now it uses nqp:: ops.
Add Thread.pm to MoarVM build.

No, don't expect it to work yet.
Merge branch 'nom' of github.com:rakudo/rakudo into eleven
Use ReentrantMutex REPR and new ops for Lock.

Means it is no longer tied to the JVM.
Move Lock.pm out of src/vm, now it's VM-generic.
Add Lock.pm to Rakudo Moar build.

With this we pass S17-concurrency/lock.t under Moar.
Add Scheduler role to the build.

Doesn't contain anything JVM-specific already.
first (nonworking) draft of Semaphore class