In C++, a function declaration with an empty parameter list means that
the function takes no arguments. In C, however, it means that the
function takes an unspecified number of parameters.
What we did previously was therefore non-conforming. This caused a
config check to fail in the curl port, as it was able to redeclare
`rand` as taking an int parameter.
The C standard states that these symbols should be declared as macros,
not as emum variants as we were doing previously. This is used in some
ports (e.g. bash) to conditionally compile locale-dependent
functionality.
We now use the same trick here as with the errno constants. We keep the
enum, but also create macros that defer to the enum variants.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
