Use -FS with VS 2013

Change-Id: I31cb7aec1a48b7b052f104ea3558cb13595a3687
chmod -x

Change-Id: Ia39ce5eeb26a11c633bc414872481d0bc08910dc
VS 2013 already has float_t

Change-Id: Ibf6f1d60fc7ec92e24fc366dc193cbd70f13c18c
Use gb_DEBUG_CFLAGS to get -FS for VS 2013

Change-Id: I22485919713f5cafb494992a36c5ada21bdcc18c
Handle VCVER==120 (VS 2013) too

Change-Id: I4dbf663790bd8906ef8b123a01bdf52e0c0c1962