Revert "headers: Move IP_MREQ from _ip_mreq1.h to ws2ipdef.h."

This reverts commit 0c7108c439fcf349ec172843b022ccec5cef5da4
This revert fixes the build of SDL_net for x86 architecture.

Signed-off-by: Biswapriyo Nath <nathbappai@gmail.com>
Signed-off-by: Liu Hao <lh_mouse@126.com>
2 files changed