If there was an error, file_url isn't exist
Added unset __STRICT_ANSI__ for MinGW

On MinGW when you set something to -std=c99 it sets __STRICT_ANSI__
which does not work with a lot of deps on clibs. So we need to turn it
off.
Merge pull request #40 from dubcanada/master

A few more fixes for Windows - MinGW