Always use our getaddrinfo.c on Windows.
Commit
a16bac36eca8158cbf78987e95376f610095f792 let "configure" detect
the system getaddrinfo() when building under 64-bit MinGW-w64. However,
src/include/port/win32/sys/socket.h assumes all native Windows
configurations use our replacement. This change placates buildfarm
member jacana until we establish a plan for getaddrinfo() on Windows.