pq/signal() portability patch. Also psql copy prompt fix.

src/backend/bootstrap/bootstrap.c

src/backend/libpq/pqcomm.c

src/backend/libpq/pqsignal.c

src/backend/postmaster/postmaster.c

src/backend/storage/lmgr/proc.c

src/backend/tcop/postgres.c

src/bin/psql/psql.c

src/include/config.h

src/include/libpq/pqsignal.h

src/interfaces/libpq/fe-exec.c

src/interfaces/libpq/pqsignal.c

src/interfaces/libpq/pqsignal.h