LibraryLookup::ofDefault leaks symbols from loaded libraries

On Windows and Mac, default lookup allows looking up symbols from any loaded library in the process. On Linux, it does not work that way. We need a stable, portable solution for default lookup.

One of the main reasons for default lookup is to allow uses to use standard C runtime library functions (from stdlib.h, stdio.h, math.h etc.) without having to load platform specific C runtime library / libraries.