[hm] Slightly simplify RF SPI setup
[hm] Remove logging "level" from HMLG. Everything uses 0 anyway
[hm] Add adc_noise.h

Tests the ADC to see how much noise there is by running in freerunning mode for 4ms
[hm] Reduce ADC noise samples to 255

Forgot that ADC takes 13 cycles, not 1, so was actually taking 54ms
instead of 4ms. I only strictly need 2 PWM cycles anyway.
[hm] Remove GRILLPID_FAN_BOOST_ENABLED and always disable PWM while reading temp

Really reduces noise when blower is running. The servo however still
may be a problem because it stays powered up.
[hm] Move noise test to grillpid

Might not be the greatest place because now lmremote compile will fail
[hm] Stop disabling fan while reading, instead only read mid-PWM cycle

This doesn't guarantee we won't read when the PWM flips on (due to
interrupts) but it works almost all the time. The old method gimped
the blower output too much by being off up to 224ms out of every 1s period.

Also fixes compile error about pid not being defined.
[hm] Update /sp docs to include manual mode info
[hm] Update fn= documentation, thanks Steve_M
[hm] Replace eeprom_X_block with local versions to save 392 bytes

avr-libc is built with prologue/epilogue so avoid including
that for such a small function.
[avr] Rename econfig.cpp econfig.c
Add LICENSE for code by Bryan Mayland - MIT License
[hm] Fix fan speed changing while alarm is sounding

tone() uses TIMER2 to generate its output and modifies the waveform
generation to do so. Because the blower uses hardware PWM on TIMER2,
this makes the blower run full on or off while the alarm is ringing.

This code fixes the alarm output at 4KHz and uses TIMER1's COMPA
vector to do the timing (same timer used for the servo output).
The new code modifiest the timer mode from normal to CTC with ICR1
as TOP which reduces the amout of code in the COMPB vector to a
single line.

Thanks to Peter F for finding the bug
[hm] Switch fan PWM to Fast PWM so we can reliably not analog sample around the turnon
[hm] Stop the servo from jerking past the end on startup, quick fix
[hm] Add tone_4khz.* to project
[hm] Version 20140320 23780 bytes