feature: C89 adherence #70

Job	Run time
Build C89 (5.1.5)	17s
Build C++ (5.1.5)	19s
Build C89 (5.2.4)	17s
Build (5.1, windows-latest)	2m 56s
Build C++ (5.2.4)	16s
MSYS2 Build (mingw64, x86_64, 5.4, lua, lua)	1m 0s
Build C89 (5.3.6)	23s
Build (5.1, ubuntu-latest)	2m 26s
Build C++ (5.3.6)	21s
MSYS2 Build (mingw64, x86_64, 5.3, lua53, lua5.3)	54s
Build C89 (5.4.7)	22s
Build (5.1, macos-latest)	2m 40s
Build C++ (5.4.7)	25s
MSYS2 Build (mingw64, x86_64, 5.1, lua51, lua5.1)	1m 0s
Build (5.2, windows-latest)	2m 43s
MSYS2 Build (mingw64, x86_64, 5.1, luajit, luajit)	1m 4s
Build (5.2, ubuntu-latest)	2m 26s
MSYS2 Build (ucrt64, ucrt-x86_64, 5.4, lua, lua)	1m 19s
MSYS2 Build (ucrt64, ucrt-x86_64, 5.3, lua53, lua5.3)	1m 0s
MSYS2 Build (ucrt64, ucrt-x86_64, 5.1, lua51, lua5.1)	1m 3s
Build (5.2, macos-latest)	2m 35s
MSYS2 Build (ucrt64, ucrt-x86_64, 5.1, luajit, luajit)	59s
Build (5.3, windows-latest)	2m 51s
MSYS2 Build (clang64, clang-x86_64, 5.4, lua, lua)	1m 32s
Build (5.3, ubuntu-latest)	2m 39s
MSYS2 Build (clang64, clang-x86_64, 5.3, lua53, lua5.3)	1m 18s
Build (5.3, macos-latest)	2m 38s
MSYS2 Build (clang64, clang-x86_64, 5.1, lua51, lua5.1)	1m 20s
Build (5.4, windows-latest)	3m 4s
MSYS2 Build (clang64, clang-x86_64, 5.1, luajit, luajit)	1m 12s
Build (5.4, ubuntu-latest)	2m 28s
Build (5.4, macos-latest)	2m 42s
Build (luajit, windows-latest)	3m 0s
Build (luajit, ubuntu-latest)	2m 35s
Upload rockspec	0s
	54m 4s

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