rtl_power: exact size bins, refactoring
rtl_power: adjustable sample rate
rtl_power: multiple frequency ranges
rtl_power: linear output
r82xx: improved tuner precision

Improve tuner precision by calculating the VCO divisor at full precision,
not at kHz resolution. Also replace the manual divison loop with a
simpler fixed-point calculation.
rtl_fm: bugfix from M. Curtis
rtl_fm: in-place demodulators
rtl_fm: no-copy architecture
r82xx: direct sampling fixes from tejeez
rtl_test: generic tuner range test

This scans 0 - 3GHz looking for frequencies that can be tuned to without
error, and refines the band edges further once a tuneable band is found. It
should work with any tuner that correctly reports tuning errors. It takes
about 1.5 minutes to complete on a R820T.
r82xx: enforce PLL register limits.

This fixes out-of-range frequencies that would set the PLL
registers to incorrect values rather than failing outright.