move imageio/example_util.[hc] (back to) examples/

decoding and file i/o have been split to imageio, all that remains is
some string routines used for parameter parsing in the examples

Change-Id: I77386cd8aa39124b9e14c95fdbaa17ea4ab5bb24

build.gradle

@@ -248,7 +248,7 @@ model {
       sources {
         c {
           source {
-            srcDir "./imageio"
+            srcDir "./examples"
             include "example_util.c"
           }
         }