Prefer `using` over `typedef` for defining aliases

Reason

Improved readability: With using, the new name comes first rather than being embedded somewhere in a declaration. Generality: using can be used for template aliases, whereas typedefs can't easily be templates. Uniformity: using is syntactically similar to auto.

Example

typedef int (*PFI)(int);   // OK, but convoluted

using PFI2 = int (*)(int);   // OK, preferred

template<typename T>
typedef int (*PFT)(T);      // error

template<typename T>
using PFT2 = int (*)(T);   // OK

Enforcement

• Flag uses of typedef. This will give a lot of "hits" :-(