Less C89, most const, static funcs
Will have to do this in a few passes for other files, but generally we:

1.  Are removing C89 style variable declarations at the top of functions
2. Adding `const` qualifiers where we can
3. Making more functions static that aren't intended to be linked outside of their translation unit

Point 1 helps with code readability, Point 2 can help with code safety and compiler optimization. Point 3 helps with code structure and makes functions "local" to their translaction unit instead of "global"
Thanks @WillAyd 