Fix typos in docs and comments

Examples/test-suite/cffi/Makefile.in

@@ -43,7 +43,7 @@ run_testcase = \
 	  env LD_LIBRARY_PATH=.:$$LD_LIBRARY_PATH $(RUNTOOL) $(CFFI) -batch -s $(SCRIPTDIR)/$(SCRIPTPREFIX)$*$(SCRIPTSUFFIX); \
 	fi
 
-# Clean: (does nothing, we dont generate extra cffi code)
+# Clean: (does nothing, we don't generate extra cffi code)
 %.clean:
 	@exit 0
 

Examples/test-suite/derived_byvalue.i

@@ -83,7 +83,7 @@ Hash {
   and by checking the typemaps.
   The typemap code also calls SwigType_remember(), if your typemaps
   defined an object type, it will be added into the SwigType table.
-  its normally a 
+  it's normally a
     SWIG_ConvertPtr(....$descriptor...)
   when it should have been a $&descriptor or $*descriptor
     

Examples/test-suite/director_exception.i

@@ -48,7 +48,7 @@ namespace Swig {
 %feature("director:except") {
   jthrowable $error = jenv->ExceptionOccurred();
   if ($error) {
-    // Dont clear exception, still be active when return to java execution
+    // Don't clear exception, still be active when return to java execution
     // Essentially ignore exception occurred -- old behavior.
     return $null;
   }

Examples/test-suite/lua/Makefile.in

@@ -53,7 +53,7 @@ run_testcase = \
 	  env LUA_PATH="$(srcdir)/?.lua;" $(RUNTOOL) $(LUA) $(SCRIPTDIR)/$(SCRIPTPREFIX)$*$(SCRIPTSUFFIX); \
 	fi
 
-# Clean: (does nothing, we dont generate extra lua code)
+# Clean: (does nothing, we don't generate extra lua code)
 %.clean:
 	@exit 0