Update polymorph.c

1. Addresses of getenv("SHELL") and system() are written to the file 'addresses' in the same working directory, it will be used by 
python driver 'bench_tester.py'
2. Address of shellstr (which is always located in the same memory on 32-bit architecture) is written to file 'adresses_ASLR_ON' in the same working directory. This file will be used by python driver 'bench_tester.py' when ASLR is ON. 
shellstr is declared as a global variable
char shellstr[] = "/bin/sh";