asm: interp_8tap_hv_pp_8x8() for Interpolate_HV_8x8
disable interpolate horizontal merge

we need width is multiple of 4 in asm code, the maskmovq is very expensive
replace pointer to coeff by coeffIdx in ipfilter_sp
asm: interp_8tap_v_sp for ipfilter_sp[FILTER_V_S_P_8]
use correct _WIN32 build guard
vec: fix VC9 build with ASM disabled but intrinsics enabled