I tried to use the new c++11 syntax with the default string class from arduino. Actually it fails because it has no begin or end.

Test-IDE: 1.6.8 (Win8.1 x64)
Board: Uno

Example code:

String temp = "abc";
for (auto tempchar : temp) {
 Serial.println(tempchar);
}

Error:

error: 'begin' was not declared in this scope
for (auto tempchar : temp) {
error: 'end' was not declared in this scope

Reference:
http://en.cppreference.com/w/cpp/language/range-for

Best