The so-called "inferred_X_fifo" are basically generics fifos using
inferred rams blocks from altera or xilinx, depending the target
platform. That's why it makes more sense to move them to the "generic"
folder of genrams. This change forces to rename the "generic_X_fifo"
under "altera". Since these fifos are using the altera fifo  Megafunction,
are going to be called "altera_X_fifo". The Manifest has been changed accordingly.

Conflicts:

	modules/genrams/xilinx/Manifest.py
	modules/genrams/xilinx/generic_dpram_sameclock.vhd
	modules/genrams/xilinx/spartan6/generic_sync_fifo.vhd