Stop using the __ANDROID_API_x__ constants.

Historically we've made a few mistakes where they haven't matched the
right number. And most non-Googlers are much more familiar with the
numbers, so it seems to make sense to rely more on them. Especially in
header files, which we actually expect real people to have to read from
time to time.

Test: treehugger
Change-Id: I0d4a97454ee108de1d32f21df285315c5488d886
diff --git a/libc/include/bits/fortify/fcntl.h b/libc/include/bits/fortify/fcntl.h
index 3c5a037..7063541 100644
--- a/libc/include/bits/fortify/fcntl.h
+++ b/libc/include/bits/fortify/fcntl.h
@@ -59,7 +59,7 @@
 int open(const char* const __pass_object_size pathname, int flags)
         __overloadable
         __clang_error_if(__open_modes_useful(flags), "'open' " __open_too_few_args_error) {
-#if __ANDROID_API__ >= __ANDROID_API_J_MR1__ && __BIONIC_FORTIFY_RUNTIME_CHECKS_ENABLED
+#if __ANDROID_API__ >= 17 && __BIONIC_FORTIFY_RUNTIME_CHECKS_ENABLED
     return __open_2(pathname, flags);
 #else
     return __open_real(pathname, flags);
@@ -83,7 +83,7 @@
 int openat(int dirfd, const char* const __pass_object_size pathname, int flags)
         __overloadable
         __clang_error_if(__open_modes_useful(flags), "'openat' " __open_too_few_args_error) {
-#if __ANDROID_API__ >= __ANDROID_API_J_MR1__ && __BIONIC_FORTIFY_RUNTIME_CHECKS_ENABLED
+#if __ANDROID_API__ >= 17 && __BIONIC_FORTIFY_RUNTIME_CHECKS_ENABLED
     return __openat_2(dirfd, pathname, flags);
 #else
     return __openat_real(dirfd, pathname, flags);
@@ -98,7 +98,7 @@
     return __openat_real(dirfd, pathname, flags, modes);
 }
 
-#if __ANDROID_API__ >= __ANDROID_API_L__
+#if __ANDROID_API__ >= 21
 /* Note that open == open64, so we reuse those bits in the open64 variants below.  */
 
 __BIONIC_ERROR_FUNCTION_VISIBILITY
@@ -139,7 +139,7 @@
                            "'openat64' " __open_useless_modes_warning) {
     return openat(dirfd, pathname, flags, modes);
 }
-#endif /* __ANDROID_API__ >= __ANDROID_API_L__ */
+#endif /* __ANDROID_API__ >= 21 */
 
 #undef __open_too_many_args_error
 #undef __open_too_few_args_error