Add __INTRODUCED_IN to core <android/*.h> APIs.

Bug: https://github.com/android-ndk/ndk/issues/706
Test: builds
Change-Id: I23db5a2180517045bafabe6fbf783456cbddf21a
Exempt-From-Owner-Approval: cherrypick
(cherry picked from commit 9db409b053460e065cefb1d1caefe048f90cfff0)
diff --git a/include/android/configuration.h b/include/android/configuration.h
index 6287332..81aedca 100644
--- a/include/android/configuration.h
+++ b/include/android/configuration.h
@@ -30,6 +30,10 @@
 
 #include <android/asset_manager.h>
 
+#if !defined(__INTRODUCED_IN)
+#define __INTRODUCED_IN(__api_level) /* nothing */
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -671,53 +675,49 @@
  */
 void AConfiguration_setUiModeNight(AConfiguration* config, int32_t uiModeNight);
 
-#if __ANDROID_API__ >= 13
 /**
  * Return the current configuration screen width in dp units, or
  * ACONFIGURATION_SCREEN_WIDTH_DP_ANY if not set.
  */
-int32_t AConfiguration_getScreenWidthDp(AConfiguration* config);
+int32_t AConfiguration_getScreenWidthDp(AConfiguration* config) __INTRODUCED_IN(13);
 
 /**
  * Set the configuration's current screen width in dp units.
  */
-void AConfiguration_setScreenWidthDp(AConfiguration* config, int32_t value);
+void AConfiguration_setScreenWidthDp(AConfiguration* config, int32_t value) __INTRODUCED_IN(13);
 
 /**
  * Return the current configuration screen height in dp units, or
  * ACONFIGURATION_SCREEN_HEIGHT_DP_ANY if not set.
  */
-int32_t AConfiguration_getScreenHeightDp(AConfiguration* config);
+int32_t AConfiguration_getScreenHeightDp(AConfiguration* config) __INTRODUCED_IN(13);
 
 /**
  * Set the configuration's current screen width in dp units.
  */
-void AConfiguration_setScreenHeightDp(AConfiguration* config, int32_t value);
+void AConfiguration_setScreenHeightDp(AConfiguration* config, int32_t value) __INTRODUCED_IN(13);
 
 /**
  * Return the configuration's smallest screen width in dp units, or
  * ACONFIGURATION_SMALLEST_SCREEN_WIDTH_DP_ANY if not set.
  */
-int32_t AConfiguration_getSmallestScreenWidthDp(AConfiguration* config);
+int32_t AConfiguration_getSmallestScreenWidthDp(AConfiguration* config) __INTRODUCED_IN(13);
 
 /**
  * Set the configuration's smallest screen width in dp units.
  */
-void AConfiguration_setSmallestScreenWidthDp(AConfiguration* config, int32_t value);
-#endif /* __ANDROID_API__ >= 13 */
+void AConfiguration_setSmallestScreenWidthDp(AConfiguration* config, int32_t value) __INTRODUCED_IN(13);
 
-#if __ANDROID_API__ >= 17
 /**
  * Return the configuration's layout direction, or
  * ACONFIGURATION_LAYOUTDIR_ANY if not set.
  */
-int32_t AConfiguration_getLayoutDirection(AConfiguration* config);
+int32_t AConfiguration_getLayoutDirection(AConfiguration* config) __INTRODUCED_IN(17);
 
 /**
  * Set the configuration's layout direction.
  */
-void AConfiguration_setLayoutDirection(AConfiguration* config, int32_t value);
-#endif /* __ANDROID_API__ >= 17 */
+void AConfiguration_setLayoutDirection(AConfiguration* config, int32_t value) __INTRODUCED_IN(17);
 
 /**
  * Perform a diff between two configurations.  Returns a bit mask of