examples/clkcount: allow command line override of spin-for-jumper
bmp085: acknowledge Bosch copyright on algorithm
chips/ds3231: add DS3231 RTC chip support and basic example
i2c: fix timing-sensitive stop precondition

I2C reads require transmitting a STOP condition prior to reading the last
data byte, to prevent the sender from transmitting another byte.  When the
read request is for a single byte, the STOP condition must be delayed until
the START condition has completed.  The previous implementation checked
incomplete START on all received bytes, not just single-byte receives, and
checked for errors before checking for the condition, which caused the STOP
to be transmitted too late for some low-speed systems.

This commit simply records the recommended fix.  The whole I2C error
recovery infrastructure will be replaced in a fix to issue #56.
eusci: documentation update

Functions are not specific to the EUSCI-A peripheral; they also function
(where supported) on EUSCI-B.
close #57: add lighter-weight serial reset

Add vBSP430serialSetReset_ni() to just manage the reset without waiting for
pending activity to complete or reconfiguring peripheral pins.
hih6130: update to use serial reset feature

Place I2C peripheral into reset when not using it; test only to validate
functionality, but should also provide lower sleep current.
Fix indentation
example/periph/i2c: add

Test framework for introspecting I2C status during various operations.
serial: note that i2c functions work only for single master configurations

Multi-master and slave configurations require different STT/STP management.
close #56: improve I2C diagnostics

Encode status information in negative error codes.  Document that functions
wil not return -1.  Make consistent that functions spin awaiting not-busy
rather than for a stop condition to be transmitted.  This may result in a
behavior difference in edge cases.
examples: minor updates to feed back I2C diagnostics
close #58: remove unnecessary RF interfaces

Replaced CC2500 with CC110X.  Keeping CC1125 for now; compatible radios are
CC1120, CC1125, CC1175, and CC1200; incompatible ones are CC110L, CC113L,
CC115L.  If whoever at TI responsible for specifying those product numbers
is replaced, it may be that they'll stop confusing everybody and make the
high-performance line's canonical model series CC120x.  Too early to tell.
Cleanup documentation goofs