Add fdatasync,pread,pwrite support to osx

Author: bvinc

examples/basic/main

@@ -46,6 +46,8 @@ package sqlite3
 
 #cgo linux,!android CFLAGS: -DHAVE_FDATASYNC=1
 #cgo linux,!android CFLAGS: -DHAVE_PREAD=1 -DHAVE_PWRITE=1
+#cgo darwin CFLAGS: -DHAVE_FDATASYNC=1
+#cgo darwin CFLAGS: -DHAVE_PREAD=1 -DHAVE_PWRITE=1
 
 #cgo windows LDFLAGS: -Wl,-Bstatic -lwinpthread -Wl,-Bdynamic