v0.6.0-rc1

Our website received a big facelift, please check it out at https://rgbds.gbdev.io! Thanks to @ISSOtm and @avivace for the work on this.
While some pages have been moved around, all URLs under /docs have been preserved.

Deprecated:

• rgbasm -h and -L will soon become the default behavior; please use rgbasm -H and -l respectively to opt into the current behavior.
• rgbgfx -h has been renamed to the less confusing rgbgfx -Z.

Added:

• RGBGFX has been massively overhauled! Please check out the new docs for full details, but notably:
  • The alpha channel is now handled in a sensible and useful way.
  • Palettes can be manually specified without having to muck with PNG embedded palettes using -c!
  • rgbgfx -r can also "reverse" the process and generate a PNG from the binary data.
  • "At-files" allow storing the flags e.g. next to the image, instead of centralized within your Makefile/build script.
  • State-of-the-art packing algorithm ensures optimal palette generation 😎
  • Special thanks to @aaaaaa123456789 for randtilegen, used for testing; @eievui5, @MarkSixtyFour, and @Rangi42 for review and testing!
  • There's an egg somewhere in there?
• Unsigned right shift operator >>>!
• Binary AND & can now be constant if applied to a symbol with the right alignment.
• RGBLINK will now report floating sections' names when using -O.
• OPT r
• A .clang-format, though it it only applied to C++ files; we are gradually transitioning away from checkpatch style.

Removed:

• PRINTT, PRINTI, PRINTV, PRINTF (use PRINT/PRINTLN instead)
• _PI
• SET as an assignment operator (use = instead)
• rgbgfx -D, -f, and -F were not useful anymore

Changed:

• man pages are now all in a single directory; this affects the release tarballs!

Fixed:

• rgblink -S rejected a lot of valid arguments.
• rgblink -O could "forget" ROM0 if no such sections were defined, offsetting the entire file.
• Whitespace is now trimmed in macro arguments, even after line continuations.
• All *UTC* symbols could contain local time instead on some systems.
• contrib/gbdiff.bash correctly handles spaces in its arguments (oops)
• Version number will always be properly updated when building with CMake.
• Math equations could render incorrectly in rgbasm(5).
• RGBDS should be portable to more systems now.
• RGBASM has been optimized slightly yet again.