imgcodecs(bmp): limit size of processed images

2Gb+ images can't be handled properly by current implementation

ozz-fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=13295

modules/imgcodecs/src/grfmt_bmp.cpp

@@ -203,6 +203,9 @@ bool  BmpDecoder::readData( Mat& img )
     int  nch = color ? 3 : 1;
     int  y, width3 = m_width*nch;
 
+    // FIXIT: use safe pointer arithmetic (avoid 'int'), use size_t, intptr_t, etc
+    CV_Assert(((uint64)m_height * m_width * nch < (CV_BIG_UINT(1) << 30)) && "BMP reader implementation doesn't support large images >= 1Gb");
+
     if( m_offset < 0 || !m_strm.isOpened())
         return false;