Basic Debian/Ubuntu package

Adding initial spec to build from source

minor configure.ac simplifications

please add AC_CHECK_LIB([ssl], [function-name]) to configure.ac in the case of failed linkage

fix unused write result in undefined HAVE_EXECINFO_H case

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