Enable syntax highlighting for template files (.t**)

Qt Creator doesn't recognize the extensions of c++ files commonly used for template code (extensions: .t** => .tcc .tpp .t++). Files with these extensions are opened as ordinary text files without syntax highlighting enabled.

These .t** are used for large amounts of template code which is not supposed to be included in header files (.h**) but obviously can't be placed in normal body files (.c**) because as template code it can't be linked via object files (.o).
Projects like gcc (libstdc++) are using the .tcc extension for example.

Related: http://developer.qt.nokia.com/forums/viewthread/296/