dynload darwin/mach-o update: - removed unnecessarily complex darwin loader interface, and sharing with dynload_unix now - mach-o symbol resolving refactored: * to handle symlinks, relative paths, paths with random casing * loading lib when not already loaded, for API consistency with ELF and PE implementations

This tests arm/thumb interwork.
Run build.sh from top-level build directory.

1. dyncall is compiled as default using Makefile-default.config
2. tests are compiled with -mthumb using Makefile-thumb.config