Fixed WIO build error; does not support IOStream::Device::empty().
Merge branch 'master' of github.com:mikaelpatel/Cosa
Time and RTC changes

* Add RTC::micros mutator - This will also allow other clock-correction
techniques.  Perhaps the current correction technique should be made
external to RTC: it only makes `seconds` as accurate as the crystal, it
imposes the overhead on a majority of apps that don't care about
`seconds` accuracy, and it may make a better clock-correction technique
more difficult.
* Add packed to time_t - Allows time_t to be a member of a packed
struct, like gps_fix_t.
* Add `const` to `IOStream & operator<<( time_t &)` - Allows it to work
on const time_t instead of implicitly casting to long clock_t.  Perhaps
this should be considered for other `IOStream & operator <<`.
*Minor change in OVF IRQ - Set `s_ticks` just once.
Merge pull request #264 from SlashDevin/Timer

Time and RTC changes
Merge branch 'master' of github.com:mikaelpatel/Cosa
Allow eeprom upload on caterina bootloader devices (leonardo, micro, etc).
First proposal.
Space between gap and separator.
Enhance helper macros and apply everywhere.
Merge pull request #268 from jediunix/aligned-shell-help

Aligned shell help
Fix make size checking

If a build is successful and required flash size was ok it creates a
file with a suffix of ‘.sizeok’. This is used to allow uploads later.
If the application grows and subsequent build exceeds the size limit
the ‘.sizeok’ file was NOT removed resulting in an upload that
overwrites the bootloader.  ‘.sizeok’ was only being removed via
‘clean’.  The fix now removes ‘.sizeok’ correctly.
Implement expires_in() for Alarm.

Useful to find out how much time is left on an alarm.
Merge pull request #269 from jediunix/fix-make-size-check

Fix make size checking
Fix first time and add to test.
Return 0 when alarm is disabled.
Set RTC just before rollover.

Time in Alarm must be kept consistent.  Any existing Alarm objects will
not work unless they are told again what the interval is.  More serious
redesign is needed and is left to another issue…
Fix USB for 8mhz atmega32u4

Tested on both 16 & 8.
Merge pull request #271 from jediunix/fix-8mhz-usb

Fix USB for 8mhz atmega32u4
Merge pull request #270 from jediunix/alarm-expires-in

Implement expires_in() for Alarm.
Add 8 MHz Pro Mini to boards.