SEQ_transform_sequence_can_be_translated, SEQ_transform_single_image_check,
SEQ_can_use_proxy can all trivially take const Sequence argument.
Made SEQ_give_frame_index take const Sequence too, by removing the
"modify seq strobe to be at least 1.0" code. The strobe itself is only
ever used inside the same function, and is already guarded by
"is strobe > 1.0" check.
Original code seems to be coming all the way from 2009 with
commit message "2.5. 12k lines of sequencer back!" (03fc5696dc).
Pull Request: https://projects.blender.org/blender/blender/pulls/126021
Match function and declaration names, picking names based on
consistency with related code & clarity.
Also changes for old conventions, missed in previous cleanups:
- name -> filepath
- tname -> newname
- maxlen -> maxncpy
Also remove const for non-pointer arguments which is meaningless in
the declaration, move a scene enum to the "enums.hh" header, and add
missing forward declaration of structs.
