Fix include path only being copied when the first includepath directive (fixes #30).

[jameswilddev]

The token was copied to a new buffer only when the first .includepath directive; this meant that subsequent .includepath directives would add what appears to be a reused buffer to the linked list of include paths, and when it came to look up a path, random text would be in that linked list and lookups would fail.

[Ro5bert]

Thank you for the fix and the test.