Add yag00's String Obfuscation pass

[Fuzion24]

This iterates over all of the global variables, adds a ciphered version of the strings, iterates over all the instructions and replaces references to the global variables with a function to decipher the string.

It seems to work well for me:

➜  build git:(yag00/StringObfuscation) ✗ cat /tmp/test.c
#include <stdio.h>

 const char * worldHi = "whatup, world";

int main(void){
  printf("Hello, there\n");
  printf("%s\n", worldHi);
  return 0;
}
➜  build git:(yag00/StringObfuscation) ✗ bin/clang -mllvm -xse /tmp/test.c
➜  build git:(yag00/StringObfuscation) ✗ ./a.out
Hello, there
whatup, world
➜  build git:(yag00/StringObfuscation) ✗ strings a.out
5]YEV$
*9/mi