Runtime support for CFI

Control Flow Integrity support in bionic.

General design:
http://clang.llvm.org/docs/ControlFlowIntegrityDesign.html#shared-library-support

This CL implements subsections "CFI Shadow" and "CFI_SlowPath" in the above document.

Bug: 22033465
Test: bionic device tests
Change-Id: I14dfea630de468eb5620e7f55f92b1397ba06217
diff --git a/libdl/libdl.arm.map b/libdl/libdl.arm.map
index 1fdc1a7..f452641 100644
--- a/libdl/libdl.arm.map
+++ b/libdl/libdl.arm.map
@@ -36,6 +36,9 @@
 
 LIBC_PLATFORM {
   global:
+    __cfi_init;
+    __cfi_slowpath;
+    __cfi_slowpath_diag;
     android_dlwarning;
     android_get_application_target_sdk_version;
     android_set_application_target_sdk_version;