Fix typos

Closes #1402.
diff --git a/examples/boing.c b/examples/boing.c
index 45c867f..5b8e667 100644
--- a/examples/boing.c
+++ b/examples/boing.c
@@ -302,7 +302,7 @@
  * The Boing ball is sphere in which each facet is a rectangle.
  * Facet colors alternate between red and white.
  * The ball is built by stacking latitudinal circles.  Each circle is composed
- * of a widely-separated set of points, so that each facet is noticably large.
+ * of a widely-separated set of points, so that each facet is noticeably large.
  *****************************************************************************/
 void DrawBoingBall( void )
 {
@@ -446,7 +446,7 @@
    static int colorToggle = 0;
 
   /*
-   * Iterate thru the points of a latitude circle.
+   * Iterate through the points of a latitude circle.
    * A latitude circle is a 2D set of X,Z points.
    */
    for ( lat_deg = 0;
diff --git a/src/osmesa_context.c b/src/osmesa_context.c
index a7de33f..03651eb 100644
--- a/src/osmesa_context.c
+++ b/src/osmesa_context.c
@@ -240,7 +240,7 @@
         if (ctxconfig->forward)
         {
             _glfwInputError(GLFW_VERSION_UNAVAILABLE,
-                            "OSMesa: Foward-compatible contexts not supported");
+                            "OSMesa: Forward-compatible contexts not supported");
             return GLFW_FALSE;
         }