Merge pull request #1 from yallop/ocamlmklib-link-flags

Use -cclib to pass linker flags via ocamlmklib.
Merge pull request #196 from whitequark/ocamlmklib

Invoke ocamldep and ocamlmklib through ocamlfind
add windows support
rewrite without pipe operator
Use -std=c99, not -std=gnu99
Simplify config extraction.
Make the variadic function test more explicit about word size.
Add dl_stubs.c and dl.ml to .gitignore.
Remove some poorly-supported POSIX types.
Simplify the platform-specific macros in posix_types_stubs.c
invoke ocamlc through ocamlfind
Merge pull request #190 from fdopen/windows

add windows support
AppVeyor: basic build configuration.
AppVeyor: patch findlib to use Unix.system instead of Unix.create_process

Unix.create_process fails with status 127 under Cygwin.
AppVeyor: build and run the tests.
use mingw ocaml
add wget
extract archive at the right location
AppVeyor: change libffi install location.
add 64-bit test