synth2 NetForLoop synthesis works a lot like begin/end blocks.

Using the synth_async_block_substatement_ makes the for-loop
synthesis properly handle the chance that there are default
inputs.
NetCondit synthesis accounts for smaller l-values

If both conditions of a NetCondit device assign to the same subset
of l-value bits, then generate a smaller NetMux device that only
switches the affected bits.
When making NetCondit objects, handle output part select.

When a mux (NetCondit) is only writing to a part of the output
vector (and using only a part of the inputs) then blend the mux
output with the previous statement output.
Sizer recognizes more LPM types.
Sanity check to prevent bad code getting through synth2 blending

When conditional ports are blending (by allowing NetPartSelects be
connected together to the outputs) make sure there isn't an accidental
overlap of drivers that invalidates the process.
Merge branch 'master' into x-sizer5