Correct spelling and typos in doxygen and comments

Signed-off-by: Dave Hickin <david.hickin@diamond.ac.uk>

testApp/misc/testSharedVector.cpp

@@ -497,8 +497,8 @@ static void testICE()
     
     D = B; // create second const reference
 
-    // clears D, but reference to B refrence
-    // to B remains, so a copy is made
+    // clears D, but reference to B
+    // remains, so a copy is made
     C = epics::pvData::thaw(D);
 
     testOk1(B.unique());