tests: add unit tests covered with Clang sanitizers

tests: add unit tests covered with Clang sanitizers

Currently we run all tests via Valgrind. This patch adds 2nd batch of
tests which are compiled with Clang AddressSanitizer[1],
LeakSanitizer[2] and UndefinedBehaviorSanitizer[3] in order to catch
more issues during QA on CI.

AddressSanitizer is a fast memory error detector.  The tool can detect
the following types of bugs:

 * Out-of-bounds accesses to heap, stack and globals
 * Use-after-free, use-after-return, use-after-scope
 * Double-free, invalid free

LeakSanitizer is a run-time memory leak detector. It can be combined
with AddressSanitizer to get both memory error and leak detection, or
used in a stand-alone mode.

UndefinedBehaviorSanitizer (UBSan) is a fast undefined behavior
detector. UBSan modifies the program at compile-time to catch various
kinds of undefined behavior during program execution, for example:

 * Using misaligned or null pointer
 * Signed integer overflow
 * Conversion to, from, or between floating-point types which would
   overflow the destination

1. http://clang.llvm.org/docs/AddressSanitizer.html
2. http://http://clang.llvm.org/docs/LeakSanitizer.html
3. http://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html

Signed-off-by: Petr Štetiar <ynezz@true.cz>