IRS_GETNAMEINFO_BUFLEN_T detection differs depending on architecture

In braches v9_11 and v9_12, IRS_GETNAMEINFO_BUFLEN_T detection in configure generates different result on the same code. This causes multilib issues. It does not allow installation of the headers both for i686 and x86_64 on the same machine for example.

Our issue on Fedora with glibc glibc-2.27 is with getnameinfo signature:

int getnameinfo(const struct sockaddr *addr, socklen_t addrlen,
                       char *host, socklen_t hostlen,
                       char *serv, socklen_t servlen, int flags);

This signature is not detected directly, but only detected as fallback. This causes the issue, because on 32-bit architectures, socklen_t is compatible with size_t, but on 64-bit architectures it is not. On 32-bit architecture, size_t is detected for IRS_GETNAMEINFO_BUFLEN_T, because it matches first.

int getnameinfo(const struct sockaddr *, socklen_t, char *,
                size_t, char *, size_t, int);

On 64-bit architecture, it has to use the fallback socklen_t.

Suggested fix is to test socklen_t types with int flags before trying size_t. The change back from unsigned int seems to be pretty old. I am aware this is already fixed in 9.13 and master.