Abstractions to compile systemlib for Linux and Nuttx

Modified uint32_t casts of pointers to unsigned long for portability.
It otherwise breaks on x86_64.

Added _PX4_IOC to handle the conflice between _IOC on Linux and NuttX.

Removed use of px4::ok() because it cannot be used in a thread based
implementation. Changed to use px4::AppMgr which uses ok() on ROS.

Removed up_cxxinitialize.c from Linux build.

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

src/modules/systemlib/param/param.c

@@ -41,7 +41,8 @@
  * and background parameter saving.
  */
 
-#include <debug.h>
+//#include <debug.h>
+#include <px4_defines.h>
 #include <string.h>
 #include <stdbool.h>
 #include <fcntl.h>
@@ -646,7 +647,7 @@ param_save_default(void)
 	const char *filename = param_get_default_file();
 
 	/* write parameters to temp file */
-	fd = open(filename, O_WRONLY | O_CREAT);
+	fd = open(filename, O_WRONLY | O_CREAT, 0x777);
 
 	if (fd < 0) {
 		warn("failed to open param file: %s", filename);