avfilter/vf_waveform: add parade display mode

Rename old parade display mode to stacked.
Signed-off-by: Paul B Mahol <onemda@gmail.com>

doc/filters.texi

@@ -13109,10 +13109,14 @@ This display mode makes it easier to spot relative differences or similarities
 in overlapping areas of the color components that are supposed to be identical,
 such as neutral whites, grays, or blacks.
 
-@item parade
+@item stack
 Display separate graph for the color components side by side in
 @code{row} mode or one below the other in @code{column} mode.
 
+@item parade
+Display separate graph for the color components side by side in
+@code{column} mode or one below the other in @code{row} mode.
+
 Using this display mode makes it easy to spot color casts in the highlights
 and shadows of an image, by comparing the contours of the top and the bottom
 graphs of each waveform. Since whites, grays, and blacks are characterized
@@ -13120,7 +13124,7 @@ by exactly equal amounts of red, green, and blue, neutral areas of the picture
 should display three waveforms of roughly equal width/height. If not, the
 correction is easy to perform by making level adjustments the three waveforms.
 @end table
-Default is @code{parade}.
+Default is @code{stack}.
 
 @item components, c
 Set which color components to display. Default is 1, which means only luminance