Vendor a 3.x version of Catch2

Everything is surely broken at this point.

tests/catch2/extras/lldbinit

@@ -0,0 +1,16 @@
+#
+# This file provides a way to skip stepping into Catch code when debugging with lldb.
+#
+# With the setting "target.process.thread.step-avoid-regexp" you can tell lldb
+# to skip functions matching the regexp
+#
+# Basically the following line tells lldb to skip all functions containing the
+# regexp "Catch", which matches the complete Catch namespace.
+# If you want to skip just some parts of the Catch code you can modify the
+# regexp accordingly.
+#
+# If you want to permanently skip stepping into Catch code copy the following
+# line into your ~/.lldbinit file
+#
+
+settings set target.process.thread.step-avoid-regexp Catch