Addresses of sections will now be added to the linkerscript via `org`, and the section name will be the path/to/file. If there is more than one section in the file, then add a @SectionName after the path/to/file to describe the section.

- add misc_constants and add joypad constants.
- rename one of the VBlank counters as it's exclusively
  used to time joypad functionality.

Signed-off-by: Tauwasser <Tauwasser@tauwasser.eu>

- Lowercase hex literals
- Lowercase rgbasm keywords (rept, endr)
- Use decimal literals by default, binary when bits are meaningful; hex indicates that it needs further review, e.g. to define a constant
- Tabs, not spaces
- Newline at end of file (rgbds sometimes complains otherwise)
- Doc comments underneath function names

Signed-off-by: Tauwasser <Tauwasser@tauwasser.eu>

This makefile can now figure graphics dependencies on its own, creates
dependency files for each compilation unit and compiles everything
separately.

This is a proposal. Please try it out, read the Makefile to see if you
get what I'm trying to do, and propose any improvements you want.