added trim operand function.

testing/zstring_test.cpp

@@ -122,5 +122,8 @@ int main(int argc, char **argv) {
    std::cout << "integer '53524534' is [" << test24 << "]" << std::endl;
    coreutils::ZString test25("-543");
    std::cout << "integer '-543' is [" << test25 << "]" << std::endl;
+
+   coreutils::ZString test26("     this is a trim test     ");
+   std::cout << "trimmed [" << test26.trim() << "]" << std::endl;
    
 }