std: get std::path tests to work again
Merge pull request #7129 from erickt/fix-std-path-tests

std: get std::path tests to work again
std::dynamic_lib: start fixing windows implementation

The code compiles and runs under windows now, but I couldn't look up any
symbol from the current executable (dlopen(NULL)), and calling looked
up external function handles doesn't seem to work correctly under windows.