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.
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