Recognize .C and .H file types as cpp

[budde25]

.C, and .H and two more valid cpp source and header types. Note the capitalization, as opposed two .c, and .h for c files.
I also found a source that mentions the extensions multiple different compilers support https://stackoverflow.com/a/3223792

[sudormrfbin]

LGTM, thank you!

[archseer]

Hmm isn't file type detection case insensitive? I think it used to be

[pascalkuthe]

It doesn't appear to be. It's just a hashmap lookup (language_config_ids_by_extension, ...) and there is no case conversion before hashmap lookup or insert. That might actually cause problems on case insensitive FS (windows)