treewide: make public headers compile with c89/c99/c11 pedantic errors #4103

Job	Run time
Compile sysdeps (dripos)	2m 17s
Compile sysdeps (lemon)	2m 22s
Build mlibc (x86_64, mlibc, gcc)	3m 40s
Compile sysdeps (aero)	2m 17s
Build mlibc (x86_64, mlibc-static, gcc)	3m 8s
Compile sysdeps (ironclad)	2m 14s
Build mlibc (x86_64, mlibc-shared, gcc)	3m 2s
Compile sysdeps (lyre)	2m 38s
Build mlibc (x86_64, mlibc-ansi-only, gcc)	2m 58s
Compile sysdeps (keyronex)	2m 23s
Build mlibc (x86_64, mlibc-headers-only, gcc)	1m 59s
Compile sysdeps (managarm)	2m 36s
Build mlibc (riscv64, mlibc, gcc)	3m 44s
Compile sysdeps (vinix)	2m 19s
Build mlibc (riscv64, mlibc-static, gcc)	4m 26s
Build mlibc (riscv64, mlibc-shared, gcc)	3m 4s
Compile sysdeps (astral)	2m 19s
Build mlibc (riscv64, mlibc-ansi-only, gcc)	2m 51s
Build mlibc (riscv64, mlibc-headers-only, gcc)	2m 4s
Build mlibc (aarch64, mlibc, gcc)	3m 57s
Build mlibc (aarch64, mlibc-static, gcc)	3m 15s
Build mlibc (aarch64, mlibc-shared, gcc)	3m 17s
Build mlibc (aarch64, mlibc-ansi-only, gcc)	2m 58s
Build mlibc (aarch64, mlibc-headers-only, gcc)	1m 54s
Build mlibc (x86, mlibc, gcc)	3m 52s
Build mlibc (x86, mlibc-static, gcc)	3m 10s
Build mlibc (x86, mlibc-shared, gcc)	3m 10s
Build mlibc (x86, mlibc-ansi-only, gcc)	3m 28s
Build mlibc (x86, mlibc-headers-only, gcc)	2m 22s
Build mlibc (m68k, mlibc, gcc)	3m 32s
Build mlibc (m68k, mlibc-static, gcc)	2m 59s
Build mlibc (m68k, mlibc-shared, gcc)	3m 0s
Build mlibc (m68k, mlibc-ansi-only, gcc)	2m 52s
Build mlibc (m68k, mlibc-headers-only, gcc)	2m 2s
Build mlibc (x86_64, mlibc, clang)	3m 14s
	1h 41m 23s

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