[markers] stroke-to-path doesn't scale stroke width used in markers

[su_v]

Applying 'Path > Stroke to Path' to a path with markers which have stroked paths in the marker definition produces incorrect results:

Visually the converted markers have a smaller appearance, in testing it seems that the separated markers after converting stroke to path do not consider the scaling of the marker stroke-width based on the stroke-width of the parent path:

Example with Arrow1M:
a) path -> stroke-width 1px, marker -> stroke-width 0.4 * 1pt
   stroke to path: marker -> stroke width 0.4 * 1pt
b) path -> stroke-width 10px, marker -> stroke-width 10 * 0.4 *1pt
   stroke to path: marker -> stroke-width 0.4 * 1pt

Steps to reproduce:
1) draw a line with 1px stroke width, add stock markers (arrow1)
2) duplicate the path, move aside and change stroke width to 10px
3) duplicate both paths, move aside and convert stroke to path
4) compare the results

Note: the result is unexpectedly or inversely (from a user's perspective) influenced by the 'Transform' setting 'Scale stroke width'.

Tested with Inkscape 0.48+devel r10098 on OS X 10.5.8 (i386)

[su_v (suv-lp)]

Test case with manually edited fill and stroke colors of the paths in the marker definitions to better visualize the difference

[su_v (suv-lp)]

Further tests show that the 'Transforms' setting: "Scale stroke width" affects the outcome - unexpectedly IMHO: the visual result of the markers should be the same when converting paths with markers to stroke, regardless of the 'Affect' setting.

[jazzynico (jazzynico)]

Reproduced on Windows XP, Inkscape trunk 10068.