Convert lib.fs to light syntax

Process:
1. Replace "(* " by "////-"
2. Replace "// OPTIMIZE" by "///OPTIMIZE"
3. Replace " o "  by " << "
4. Replace " & " by " && "
5. Use Fantomas to format the whole file
6. Recover comments into their original forms

Note:
Fantomas chokes at ('a, 'b) func type and "land", "lor" operator