Remove ALL_EXTENSION_LANGUAGES and ALL_ENABLED_EXTENSION_LANGUAGES
This removes the ALL_EXTENSION_LANGUAGES and
ALL_ENABLED_EXTENSION_LANGUAGES macros, in favor of ordinary
iterators. For ALL_ENABLED_EXTENSION_LANGUAGES, I chose to simply
inline the check, as that seemed simpler than trying to make
filtered_iterator work for std::array. (As an aside, this sort of
thing will be easier once we can use the ranges library...)
gdb/ChangeLog
2020-05-08 Tom Tromey <tom@tromey.com>