Adapt to PLATFORM_VERSION_FUTURE_CODENAMES.

Don't preserve the confusing names from make. Rename AllCodenames to
ActiveCodenames, add FutureCodenames, and add CombinedCodenames to
fetch the *real* AllCodenames.

To allow `introduced=P` in NDK library definitions, we need to know
that P exists. Use the combined list of current and future API
codenames generating stubs.

Test: make ndk
Test: check out/soong/api_levels.json
Bug: None
Change-Id: I435f9ce7446236edc268a84e33474044a55a6302
diff --git a/android/variable.go b/android/variable.go
index 8462d0d..74fa868 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -102,8 +102,9 @@
 	// Suffix to add to generated Makefiles
 	Make_suffix *string `json:",omitempty"`
 
-	Platform_sdk_version           *int     `json:",omitempty"`
-	Platform_version_all_codenames []string `json:",omitempty"`
+	Platform_sdk_version              *int     `json:",omitempty"`
+	Platform_version_active_codenames []string `json:",omitempty"`
+	Platform_version_future_codenames []string `json:",omitempty"`
 
 	DeviceName        *string   `json:",omitempty"`
 	DeviceArch        *string   `json:",omitempty"`