Fix various typos

Found via codespell

src/Mod/CAM/Path/Op/Vcarve.py

@@ -164,7 +164,7 @@ class _Geometry(object):
 
     def incrementStepDownDepth(self, maximumUsableDepth):
         """
-        Increase stepDown depth before staring new carving pass.
+        Increase stepDown depth before starting new carving pass.
         :returns: True if successful, False if maximum depth achieved
         """
 

src/Mod/CAM/libarea/clipper.cpp

@@ -1903,7 +1903,7 @@ bool Clipper::ExecuteInternal()
 void Clipper::SetWindingCount(TEdge& edge)
 {
     TEdge* e = edge.PrevInAEL;
-    // find the edge of the same polytype that immediately preceeds 'edge' in AEL
+    // find the edge of the same polytype that immediately precedes 'edge' in AEL
     while (e && ((e->PolyTyp != edge.PolyTyp) || (e->WindDelta == 0))) {
         e = e->PrevInAEL;
     }
@@ -3083,7 +3083,7 @@ void Clipper::ProcessHorizontal(TEdge* horzEdge)
         while (e) {
 
             // this code block inserts extra coords into horizontal edges (in output
-            // polygons) whereever maxima touch these horizontal edges. This helps
+            // polygons) wherever maxima touch these horizontal edges. This helps
             //'simplifying' polygons (ie if the Simplify property is set).
             if (m_Maxima.size() > 0) {
                 if (dir == dLeftToRight) {

src/Mod/CAM/libarea/clipper.hpp

@@ -40,7 +40,7 @@
 // improve performance but coordinate values are limited to the range +/- 46340
 // #define use_int32
 
-// use_xyz: adds a Z member to IntPoint. Adds a minor cost to perfomance.
+// use_xyz: adds a Z member to IntPoint. Adds a minor cost to performance.
 // #define use_xyz
 
 // use_lines: Enables line clipping. Adds a very minor cost to performance.