Add missing consts for Ubuntu

Author: WyattBlue

include/libswscale/swscale.pxd

@@ -1,6 +1,4 @@
-
 cdef extern from "libswscale/swscale.h" nogil:
-
     cdef int   swscale_version()
     cdef char* swscale_configuration()
     cdef char* swscale_license()
@@ -13,7 +11,6 @@ cdef extern from "libswscale/swscale.h" nogil:
     cdef struct SwsFilter:
         pass
 
-    # Flags.
     cdef int SWS_FAST_BILINEAR
     cdef int SWS_BILINEAR
     cdef int SWS_BICUBIC
@@ -25,7 +22,6 @@ cdef extern from "libswscale/swscale.h" nogil:
     cdef int SWS_SINC
     cdef int SWS_LANCZOS
     cdef int SWS_SPLINE
-
     cdef int SWS_CS_ITU709
     cdef int SWS_CS_FCC
     cdef int SWS_CS_ITU601
@@ -41,11 +37,9 @@ cdef extern from "libswscale/swscale.h" nogil:
         int src_slice_y,
         int src_slice_h,
         unsigned char *const *dst_slice,
-        int *dst_stride,
+        const int *dst_stride,
     )
-
     cdef void sws_freeContext(SwsContext *ctx)
-
     cdef SwsContext *sws_getCachedContext(
         SwsContext *context,
         int src_width,
@@ -59,9 +53,7 @@ cdef extern from "libswscale/swscale.h" nogil:
         SwsFilter *dst_filter,
         double *param,
     )
-
-    cdef int* sws_getCoefficients(int colorspace)
-
+    cdef const int* sws_getCoefficients(int colorspace)
     cdef int sws_getColorspaceDetails(
         SwsContext *context,
         int **inv_table,
@@ -72,7 +64,6 @@ cdef extern from "libswscale/swscale.h" nogil:
         int *contrast,
         int *saturation
     )
-
     cdef int sws_setColorspaceDetails(
         SwsContext *context,
         const int inv_table[4],