spkToolbar: spkGraphTools: Patch by haword (issue #0024081) for alternative gradient painting. Avoid unnecessary calculations. Cosmetic changes. Google-translate the polish comments.

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3663 8e941d3f-bd1b-0410-a28a-d453659cc2b4