Rewrite __cxa_atexit / __cxa_finalize

Simplify:
 - Use a single memory-mapped region to hold the table of destructors.
   Double its capacity each time it is expanded.
 - Add a recompaction pass at the end of __cxa_finalize that shifts
   entries forward and uses madvise to clean pages.

Bug: http://b/148055738
Test: bionic-unit-tests
Change-Id: Ieb9da2b88640a8a5277d217b43826b5b7e246781
(cherry picked from commit afa983c8d44400d45c1f0e2b8e90a8be04acf6f7)
diff --git a/tests/Android.bp b/tests/Android.bp
index 4bd96ad..8b1eebc 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -79,6 +79,7 @@
     defaults: ["bionic_tests_defaults"],
     srcs: [
         "__aeabi_read_tp_test.cpp",
+        "__cxa_atexit_test.cpp",
         "alloca_test.cpp",
         "android_get_device_api_level.cpp",
         "arpa_inet_test.cpp",