Cygwin build: Ensure we have cross-compile environment configured for imagemagick
Cygwin build: Explicitly disable lzma in ImageMagick
Cygwin build: Fix environment switch procedure for pkg-config
Cygwin build: Revert 3f05fb2b, because it's not really required
Fine-tune interpolation type icons and using all icnos in one sif file concept to enable easy maintainance
Merge pull request #51 from morevnaproject/0.64.1

Fix Cygwin build environment
Delete unused sif interpolation type icon files
Cleanup by removing unused sif files according to the interpolation type icons update
Update canvas panel and import image layer icons

Since 0.64.0, we introduced a new icon for parameter of canvas, to have a consistant
icon metaphor, we update canvas and import image layer icons accordingly.
Add skeleton layer icon.
Add initial version of Stroboscope icon.
Correct the canvas panel icon
Use stroboscope and skeleton layer icons for layer tree
Add forbid animation icon(used in paramerter panel)
Make parameter list uses forbid animation icon instead of animate mod off icon

So that we can have consistant looking of icons for parameter panel.
Merge pull request #52 from morevnaproject/0.64.1

Icons update
Add new constructor to Vector class based on radius and angle.
When adding ducks in duckamtic, do not use the component index directly.
Get the index by name.
When calculating the reverse of a BlinePoint, use its internal reverse
member instead of figure out externally.
Refactor class BLinePoint:
1) Replace split_tangent by the combination of split_tangent_ragdius and
split_tangent_angle.
2) Add new private members to retrive the combination of both flags for
full split or full merged
3) Add two new private members to store the tangent2 to return for the
possible split flags combinations (tangent2_radius_split and tangent2_angle_split)
4) New private member function update_flags to update new flags from 2)
5) New private member to update the tangent2 accordingly to the flags.
6) Update callbacks to BLinePoint members where applicable.