mibuild/altera_quartus: use default gui command line parameters (enable pll constraints propagation) and remove deprecated methods
mibuild: expose add_period_constraint (easier to use for simple designs than vendor specific code)
mibuild/platforms: use add_period_constraint
genlib/fifo: add SyncFIFORelaxed

In some instances XST fails to map SyncFIFO to BRAM because of the
asynchronous read. This adds a FWFT FIFO that always registers dout and
should be mappable to BRAM in all cases. It also adds a bypass around
the entire thing to achieve the same behavior and latency as SyncFIFO.