Fix source comment typo

Closes #1982

(cherry picked from commit eacc1cafba90fa7b52302841dd47f5f8b1bf777a)

examples/splitview.c

@@ -2,7 +2,7 @@
 // This is an example program for the GLFW library
 //
 // The program uses a "split window" view, rendering four views of the
-// same scene in one window (e.g. uesful for 3D modelling software). This
+// same scene in one window (e.g. useful for 3D modelling software). This
 // demo uses scissors to separate the four different rendering areas from
 // each other.
 //