Linux to posix conversion

Changed "linux" target to "posix". Most of the changes are shared with
QuRT and with OSX. The Linux specific parts are in for i2c which uses
<linux/i2c.h> and <linux/i2c-dev.h>.

There is also a check for __PX4_LINUX in mavlink for a tty ioctl that is
not supported.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/modules/commander/module.mk

@@ -52,7 +52,7 @@ ifdef ($(PX4_TARGET_OS),nuttx)
 SRCS += 
 			state_machine_helper.cpp 
 else
-SRCS +=			state_machine_helper_linux.cpp 
+SRCS +=			state_machine_helper_posix.cpp 
 endif
 
 MODULE_STACKSIZE = 5000