Add android::base::ScopeGuard

Taken from bionic/libc/private/ScopeGuard.h.

Test: New unit tests
Change-Id: If83c1990efbf294aee0b5d40a7a9ac326e5e765e
diff --git a/base/Android.bp b/base/Android.bp
index 121da42..3af7686 100644
--- a/base/Android.bp
+++ b/base/Android.bp
@@ -98,6 +98,7 @@
         "parseint_test.cpp",
         "parsenetaddress_test.cpp",
         "quick_exit_test.cpp",
+        "scopeguard_test.cpp",
         "stringprintf_test.cpp",
         "strings_test.cpp",
         "test_main.cpp",