Specify parameters for all C functions. Not specifying parameters is the
same as specifying "void" in C++ and in C23 and later but that's not the
case in C prior to C23.
Compile C files with the same warnings as C++ files, additionally making
the strict prototypes warning an error to catch such problems in the
future. This commit isn't intended to address all the other warnings now
being emitted.
8f68ffd203