Include 'netinet/in_systm.h' on OpenBSD

Otherwise 'n_time' is undefined.
Drop typedef redeclarations

C99 doesn't permit redeclaring typedefs in the same scope.
Add /usr/local/{include,lib} to search paths on OpenBSD
Merge branch 'openbsd' of https://github.com/czarkoff/ProjectTox-Core into czarkoff-openbsd