add lib (some useful functions)
add SIGINT handling
Revert "add SIGINT handling"

This reverts commit 5756e6c07b1f1d2e74f2cf6166d5c6465ccbe074.
add SIGINT handling
allow reusing local address in tcp_socket()
add utils.c functions description
add parse_filename() routine
fix implicit declaration warning
add trash_create() routine
add lab3