Reordering condition checking.

Bug report: http://code.opencv.org/issues/3329

create `d_fgimg` matrix before cleaning.

In the function cvInitIntrinsicParams2D the principal point for
normalized image coordinates is set to 0/0. This updates the function
to initialize the principal point at 0.5/0.5.

"#error" requires DOS line endings (or fails with fatal error C1004: unexpected end-of-file found)
See: http://connect.microsoft.com/VisualStudio/feedback/details/794991/c-error-directive-and-unix-line-endings-leads-to-an-unexpected-end-of-file
So replace them to #pragma message.