Addresses https://cygwin.com/pipermail/cygwin/2023-March/253220.html
Take the opportunity to follow FreeBSD's and Linux's lead in recasting
macro inline code as calls to static inline functions. This allows the
macros to be type-safe. In addition, added a lower bound check to the
functions that use a cpu number to avoid a potential buffer underrun on
a bad argument. h/t to Corinna for the advice on recasting.
Fixes: 362b98b49a ("Cygwin: Implement CPU_SET(3) macros")
dfd14093e3