remove printf from signal handlers and reduce configure.ac

use AC_SEARCH_LIB in configure.ac (shorter code)
replace '-lm -lcrypto -lz' by  @LIBS@ in Makefile.in and AC_CHECK_LIB macros in configure.ac
replace NO_BACKTRACE by HAVE_EXECINFO_H

Update interface.c

Fix typo in help command

Added chat_with_peer in commands. Also explained what peer is.

Little typo error in readme

Fixed typo in linux lib install instructions in README.md

AES_KEY structure clean up

fix very small memory leaks

fix memory leak (BN_clear doesn't release allocated memory)

improve portability by removing rdtsc calls