SDL_gfx: update to 2.0.27 (revbump OpenXcom, freedroidRPG, hyperrogue)

[Rutpiv]

Testing the changes

• I tested the changes in this PR: briefly

Local build testing

• I built this PR locally for my native architecture (x86_64)
• I built this PR locally for these architectures using specific masterdirs:
  • x86_64-musl
  • i686
• I built this PR locally for these architectures (crossbuilds):
  • aarch64
  • aarch64-musl
  • armv7l
  • armv7l-musl
  • armv6l
  • armv6l-musl
  • hyperrogue was not cross-compiled

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Regenerate build system with autoreconf -vfi to fix an incorrect SONAME in the upstream tarball (shipped configure was not regenerated since 2.0.25, resulting in libSDL_gfx.so.15 instead of the correct libSDL_gfx.so.16). Update common/shlibs and revbump reverse dependencies accordingly.