Make android_get_application_target_sdk_version available to the NDK.

Also move this and android_get_device_api_level into <android/api-level.h>
so that they're always available.

This involves cleaning up <sys/cdefs.h> slightly.

Bug: N/A
Test: builds
Change-Id: I25435c55f3549cd0d827a7581bee75ea8228028b
diff --git a/libc/bionic/semaphore.cpp b/libc/bionic/semaphore.cpp
index d401b66..e0486b4 100644
--- a/libc/bionic/semaphore.cpp
+++ b/libc/bionic/semaphore.cpp
@@ -41,7 +41,6 @@
 
 #include "private/bionic_constants.h"
 #include "private/bionic_futex.h"
-#include "private/bionic_sdk_version.h"
 #include "private/bionic_time_conversions.h"
 
 // In this implementation, a semaphore contains a
@@ -222,7 +221,7 @@
     }
 
     int result = __futex_wait_ex(sem_count_ptr, shared, shared | SEMCOUNT_MINUS_ONE, false, nullptr);
-    if (bionic_get_application_target_sdk_version() >= __ANDROID_API_N__) {
+    if (android_get_application_target_sdk_version() >= __ANDROID_API_N__) {
       if (result ==-EINTR) {
         errno = EINTR;
         return -1;