std::string_view is not guaranteed to point to null-terminated string
literals, it may point to a substring of such a string or a string which
is not null-terminated.
cql_duration() constructor obtains data() pointer from std::string_view
and creates another std::string_view from it, after some conditional
pointer arithmetics. Constructing a new std::string_view from a raw
pointer, without specifying its length, will lead to strlen() being
called on the pointer, resulting in undefined behaviour if the string
is not null-terminated. Use substr() instead of pointer arithmetics to
avoid this problem altogether.
boost::regex_match() invokations also use std::string_view::data().
This leads to strlen() and heap-buffer-overflow if the string is not
null-terminated. Invoke the overload which takes an iterator pair
instead.
Not a problem on current master, as all callers pass null-terminated
strings.
