Add missing includes for integer type definitions.
Add libopencm3 as a submodule.
Add local libopencm3 to include and library path.
Add libswiftnav as a submodule.
Detect Windows and ask cmake to generate MSYS makefiles for libswiftnav.
Updated libswiftnav.
Merge pull request #5 from gsmcmullin/submodules

Include libopencm3 and libswiftnav as submodules.
Console: Fix PRN numbering off-by-one in observation view
Merge pull request #4 from henryhallam/master

Console: Fix PRN numbering off-by-one in observation view
SBP now using libswiftnav SBP implementation.

 - All callbacks updated to follow new function prototype
 - screaming_death updated to use libswiftnav SBP functions too
 - NAP hash checked from init() after sbp_setup so screaming_death
   works if hash check fails
 - Flash callbacks updated to return an error code in the
   MSG_FLASH_DONE message instead of calling screaming_death.
 - flash.py checks MSG_FLASH_DONE return code but doesn't attempt
   to handle errors properly
Merge branch 'master' of github.com:swift-nav/piksi_firmware into new_sbp
Updated all tests for new SBP code. Everything building.
Update Makefile so libopencm3 is only built for F4.