Add hello world example.
Assemblage's assemble.ml remove a useless link_all.
Assemblage API: least surprise rename ?link_all to ?linkall.
Add As_flags.vmthread.
Add threads example.
ocamldep rule: don't include pkg dependencies.

Also tries to keep local deps flags as ordered as possible.
ocamlfind resolver. Hack to compile with -thread.
Add threads-lib example.

Not formally in the test suite, we need to be able to define
bytecode only libraries first.
Fix As_shell.try_exec. POSIXly redirect any output to /dev/null.

Not only where we redirecting only stderr, &> is not POSIX
compliant which breaks on linux Sys.command.
Add As_shell.has_cmd to test for the existence of a command.
Check ocamlfind existence using As_shell.has_cmd.
Makefile: be more precise in the all target, avoid unused targets.
ocamlfind resolver: we also need includes at link time.

This may be needed for C .a lookups.
Add ctypes-libffi example. Test case for previous commit.
Remove ocamlgraph dependency in bootstrap
Merge pull request #99 from dbuenzli/threads-biz

Compiling with threads.
Merge pull request #100 from dbuenzli/fix-82

Beware of bashisms in Sys.command.
Merge pull request #102 from dbuenzli/precise-all

Precise all
Merge pull request #103 from dbuenzli/correct-link

Linking also needs the includes (for C archives lookup).
Rename As_features.not_ to As_features.neg and add conditional negation.