Enable use of TSAN

The -DWITH_TSAN option enables the ThreadSanitizer if libtsan is
installed.

cmake/FindTSAN.cmake

@@ -0,0 +1,14 @@
+# Find ThreadSanitizer libraries
+#
+# The following variables are set:
+# TSAN_FOUND - If ThreadSanitizer was found
+# TSAN_LIBRARIES - Path to the libasan library
+
+find_library(TSAN_LIBRARIES NAMES libtsan.so.0 libtsan.so.1 libtsan.so.2 libtsan.so.3 libtsan.so.4)
+
+if (TSAN_LIBRARIES)
+  message(STATUS "Found ThreadSanitizer libraries: ${TSAN_LIBRARIES}")
+  set(TSAN_FOUND TRUE CACHE INTERNAL "")
+else()
+  message(STATUS "Could not find AdressSanitizer")
+endif()