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/sensors/module.mk

@@ -41,7 +41,7 @@ MODULE_PRIORITY	= "SCHED_PRIORITY_MAX-5"
 ifeq ($(PX$_TARGET_OS),nuttx)
 SRCS		= sensors_nuttx.cpp 
 else
-SRCS		= sensors_linux.cpp 
+SRCS		= sensors_posix.cpp 
 endif
 SRCS +=		  sensor_params.c
 

src/modules/sensors/sensors_nuttx.cpp

@@ -46,7 +46,7 @@
  * @author Anton Babushkin <anton@px4.io>
  */
 
-#include <px4_config.h>
+#include <nuttx/config.h>
 
 #include <fcntl.h>
 #include <poll.h>