Squashed slave mode changes onto master.
B100: moar buffering on TX for better performance in bidirectional applications
Slave FIFO: fix for PKTEND not asserting @ end of RX.
b100: bumped fpga compat number for slave fifo mode
Fix missing B100 core_compile (poor Git hygeine)
usrp2: firmware should reset dsp on icmp pkt

1) This should kill any streaming,
the previous calls would just stop continuous streaming

2) The breaks were changed to returns
to avoid reprogramming the framer.
usrp2: same change but to fw updater
uhd: add samples per pkt option to rx streamer
usrp1/b100: handle longer reenumerations with loop and timeout
dsp rework: u2_core test implementation
dsp rework: renamed dsp signals for frontend IO
Swap I/Q on transmit
dsp rework: implemented dsp changes for other top levels

added user registers into each toplevel (not used yet)
usrp1/b100: reenumeration loop with timeout only when found
dsp rework: integrated custom dsp module shells
dsp rework: top level fixes B100/E100
dsp rework: moved scale and round into ddc chain

16to8 engine now performs only a clip from 16->8
dsp rework: added double buffer interface to vita tx
dsp rework: increase the number of effective bits in the duc scale factor

This will be useful for effecting the dynamic range of the sc8 tx mode.
dsp: 8 to 16 bit conversion for tx side.  believed to be functional