Currently, in sculpting, weight paint and vertex paint modes every cursor movement triggers redraw of a brush. During that redraw, native cursor is set. Under the hood, setting the cursor causes freeing of previous cursor and allocating a new one. In most cases, in previously mentioned modes, recreating cursor is unnecessary since cursor stays the same.

This patch adds a check which skips cursor change if requested cursor is already set. The check could be added in pain_cursor.c, but I felt adding it inside WM_cursor_set function would hopefully skip more unnecessary cursor reallocations.