Add missing stdbool.h to sensor.h.

This got hacked into the NDK headers ages ago, but never got
upstreamed to the frameworks.

Test: make checkbuild
Bug: https://github.com/android-ndk/ndk/issues/370
Change-Id: Id38cbc96633c1c61de36996c2dd9e6c2331bd6e7
diff --git a/include/android/sensor.h b/include/android/sensor.h
index cdb3fff..97b4a2a 100644
--- a/include/android/sensor.h
+++ b/include/android/sensor.h
@@ -50,6 +50,7 @@
 
 #include <android/looper.h>
 
+#include <stdbool.h>
 #include <sys/types.h>
 #include <math.h>
 #include <stdint.h>