Use C++ and C++ flags for .cpp source in libraries

.cpp files in libraries were being compiled with C and C flags which
caused compile errors when Watchdog.hh was included because it includes
Queue.h that depends on C++ for static_assert.
time_t changes for consideration

plus updates to 2 core files and 11 example programs that use time_t
Merge pull request #248 from jediunix/c++-library-compile

Use C++ and C++ flags for .cpp source in libraries
epic epoch work

Made epoch_year a static member with accessor/mutator so that different
epochs can be selected at run time.  This will allow NTP to do its
calculations WRT the NTP epoch, while the rest of the system runs on a
more-efficient epoch.
Added parse method to match operator <<.
Added use_fastest_epoch method to configure time_t to run as quickly as
possible.
Removed timing and old code comments.
Fixed minor bug at for epoch years that don't end in 00.
CosaTime now has numerous tests for clock_t conversions and performance
measurements (log file added).
Use the NTP epoch instead of the default Y2K
Merge pull request #249 from SlashDevin/time_t

time_t support for multiple epochs
Clean up.
Clean up.
Improve accuracy of RTC

The RTC clock runs fast.  At 16mhz each second is 576us fast or 9 ticks
every 16 seconds which is approximately 2 seconds per hour.  This
change accumulates the error every second and then suppresses a tick
when enough error has been accumulated.  At 16mhz this is approximately
every other second (9 every 16).

The problem and solution was verified with GPS time.  In 17 hours the
RTC is now 4 seconds slow.  This is probably due to the accuracy of my
oscillator and will require future modifications to allow disciplining
the clock from an external source.
Adding support for execution time measurement.

1. New block prefix macro MEASURE(msg,cnt) in Trace support.
2. Update benchmarks with new measurement style.
3. Update benchmark runs.
Remove compiler warning on macro redefinition.
Fixed help string for digitalwrite; did not correctly describe the options.
Refined
Merge branch 'master' of https://github.com/mikaelpatel/Cosa into RTC-accuracy
Merge pull request #250 from jediunix/RTC-accuracy

Improve accuracy of RTC
Update ATmega1284P.hh

to access pins D15 & D16
Update PinChangeInterrupt.cpp

base is given by parameters from the macro later
Update PWMPin.cpp

COM1x0 enable both, direct & complementary PWM output. COM1x1 only the direct one.
Merge pull request #253 from thomasahlendorf/patch-3

Update PWMPin.cpp
Merge pull request #251 from thomasahlendorf/patch-1

Update ATmega1284P.hh