Missing documentation for migen.genlib modules

[mithro]

The following migen.genlib modules already have inline documentation!

• coding - Good!
• sort - Good!

The following migen.genlib modules are missing docstrings or other form of inline documentation;

• [ ] cdc - BusSynchronizer has a dockstring, but others don't.
• [ ] complex - This is just a complex number? - What makes it different from Python's inbuilt complex type?
• [ ] divider - Whats "w"? The width? What is it actually dividing?
• [x] fsm - Lots of undocumented stuff here.
• [ ] io - These are mostly self explanatory, but still could use information about why they exist?
• [ ] misc - Lots of undocumented stuff here.
• [ ] record - Lots of undocumented stuff here.
• [ ] resetsync - Why does the AsyncResetSynchronizer exist?
• [ ] rob - Lots of undocumented stuff here.
• [ ] roundrobin - switch_policy?

These last two modules are mostly good but need some fixes.

• [ ] mhamgen - The documentation is all in comments rather than in Python doc strings.
• [ ] fifo - Mostly good, but how is SyncFIFOBuffered different?

As I figure out these modules I'll try and start sending patches with documentation myself if no one else has gotten to it first.

[mithro]

FYI - @ajitmathew