Last minute OpenGL fix: don't check flippedness in HWR_RotateSpritePolyToAim if the mobj is actually a precipmobj!

precipmobj_t does not have eflags, so P_MobjFlip checking it would actually be accessing memory addresses beyond the end of the struct

These fixes were suggested by Sveciaost on #mac-users on Discord

The compiler doesn't like this and will give you a "inlining failed in call to 'P_DoTwinSpin': call is unlikely and code size would grow" error

This reverts commit 2e27f32d.