Create test/testutil.h for unit test helper macros

Defines SETUP_TEST_FIXTURE and EXECUTE_TEST, and updates ssl/heartbeat_test.c
using these macros. SETUP_TEST_FIXTURE makes use of the new TEST_CASE_NAME
macro, defined to use __func__ or __FUNCTION__ on platforms that support those
symbols, or to use the file name and line number otherwise. This should fix
several reported build problems related to lack of C99 support.
test/README and test template generator
Add debug-test-64-clang Configure target

Apparently clang 3.1, which ships with FreeBSD 9.1, completely ignores
-fsanitize. Clang 3.3, which ships with FreeBSD 9.2, compiles with it, but
fails to link due to the absence of libasan:

http://lists.freebsd.org/pipermail/freebsd-hackers/2013-December/043995.html
https://www.mail-archive.com/cfe-commits@cs.uiuc.edu/msg92260.html
http://reviews.llvm.org/D2644
Add cscope and ctags files to .gitignore
Environment variables and aliases for unit testing