Document that dlclose with thread_local is fixed in P.

Bug: android/ndk#360
Test: N/A
Change-Id: Ib9807045bd3206fa3cd300ab70ebed93c73a58e4

Author: enh-google

android-changes-for-ndk-developers.md

@@ -389,16 +389,16 @@ adb shell setprop debug.ld.all dlerror,dlopen
 Android allows `dlclose` to unload a library even if there are still
 thread-local variables with non-trivial destructors. This leads to
 crashes when a thread exits and attempts to call the destructor, the
-code for which has been unloaded (as in [issue 360]).
+code for which has been unloaded (as in [issue 360], fixed in P).
 
 [issue 360]: https://github.com/android-ndk/ndk/issues/360
 
 Not calling `dlclose` or ensuring that your library has `RTLD_NODELETE`
 set (so that calls to `dlclose` don't actually unload the library)
 are possible workarounds.
 
-|                   | Pre-M                      | M+      |
-| ----------------- | -------------------------- | ------- |
-| No workaround     | Works for static STL       | Broken  |
-| `-Wl,-z,nodelete` | Works for static STL       | Works   |
-| No `dlclose`      | Works                      | Works   |
+|                   | Pre-M                      | M+      | P+    |
+| ----------------- | -------------------------- | ------- | ----- |
+| No workaround     | Works for static STL       | Broken  | Works |
+| `-Wl,-z,nodelete` | Works for static STL       | Works   | Works |
+| No `dlclose`      | Works                      | Works   | Works |