progreloc: Speed up executable lookup on various platforms. * lib/progreloc.c: Include <errno.h>. (safe_read, full_read): New functions. (find_executable): On GNU/kFreeBSD, FreeBSD, DragonFly, NetBSD, Solaris, prefer the information from the /proc file system to a PATH search.

/* Whether pipes are FIFOs; -1 if not known.  */
#ifndef HAVE_FIFO_PIPES
# define HAVE_FIFO_PIPES (-1)
#endif

int isapipe (int fd);