cannot build in linux

[andrew-davie]

We have a 'deprecated code' warning which builds under MacOS but not under Linux.
Specifically....

exp.c:645:28: warning: passing arguments to a function without a prototype is deprecated in all versions of C and is not supported in C23 [-Wdeprecated-non-prototype]

  645 |         (*Opdis[Opi]_unary)(Argstack[Argi], Argflags[Argi]);
      |                            ^

exp.c:657:29: warning: passing arguments to a function without a prototype is deprecated in all versions of C and is not supported in C23 [-Wdeprecated-non-prototype]

  657 |         (*Opdis[Opi]_binary)(Argstack[Argi], Argstack[Argi+1],
      |                             ^
2```

That's my MacOS build (which works).
Under my Linux (Ubuntu) environment, this is now flagged as an unrecoverable error and I cannot build.

This needs to be fixed; a deprecation warning should be fixed ASAP, not ignored!

[andrew-davie]

A temporary "fix" is to include "-std=c11' as a build switch.