Add support for large bom files (fixes #2)

This adds support for larger bom files (more than 512 files). I've tested this on several Mac OS X versions and it's working for me.

The fix involves putting max 256 file into one BOMPaths structure and then referencing each BOMPaths structure in a root BOMPaths (isLeaf=0) structure. The BOMPathIndices entries in the root BOMPaths point to the child BOMPaths (BOMPathIndices->index0) and to the last BOMFileInfo in that child BOMPaths (BOMPathIndices->index1).

The code could definitely use some cleanup and more testing.