warnings about common incorrect usage of exceptions

[llvmbot]

Bugzilla Link	11351
Version	2.9
OS	Linux
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor,@gribozavr

Extended Description

It would be great if clang showed warnings about common incorrect usage of exceptions and appropriate fix-it hint.

That is:

1. "throw new"
2. catch by value
3. rethrow that change exception type

#include <stdexcept>


int main()
{
    try
    {
        throw new std::runtime_error("hello, kitty!"); // warning: "throw new", fix-it: remove "new"
    }
    catch (std::exception e) // warning: catch by value, fix-it: add "const&" or "&"
    {
        throw e; // warning: rethrow change a type, fix-it: remove "e"
    }
  
    return 0;
}