This adds UNSCOPED_INFO macro, creating a log message that is stored
until the end of next assertion or the end of test case, whichever comes
first. These messages are not scoped locally, unlike messages created by
INFO macro.
The previous implemetation was just plain broken for most of
possible uses, the new one should work (even though it is ugly
as all hell, and should be improved ASAP).
Fixes#1436
Because the macro name is compile-time constant, we do not have to
worry about lifetimes and will avoid allocation in case of missing
SSO or long macro name.
