This is a description of C preprocessor defines that readline accepts.
Most are passed in from the parent `make'; e.g. from the bash source
directory.

NO_SYS_FILE		<sys/file.h> is not present
HAVE_UNISTD_H		<unistd.h> exists
HAVE_STDLIB_H		<stdlib.h> exists
HAVE_GETPW_DECLS	declarations for the getpw functions are in <pwd.h>
HAVE_VARARGS_H		<varargs.h> exists and is usable
HAVE_STRING_H		<string.h> exists
HAVE_ALLOCA_H		<alloca.h> exists and is needed for alloca()
HAVE_ALLOCA		alloca(3) or a define for it exists
PRAGMA_ALLOCA		use of alloca() requires a #pragma, as in AIX 3.x
VOID_SIGHANDLER		signal handlers are void functions
HAVE_DIRENT_H		<dirent.h> exists and is usable
HAVE_SYS_PTEM_H		<sys/ptem.h> exists 
HAVE_SYS_PTE_H		<sys/pte.h> exists 
HAVE_SYS_STREAM_H	<sys/stream.h> exists

System-specific options:

OSF1			A machine running OSF/1
BSD386			BSDI's BSD/386 version 1.0 or 1.1
NetBSD			NetBSD
FreeBSD			FreeBSD version 1.1
_386BSD			Old FreeBSD or NetBSD or ancient Jolitz 386bsd
AIX			AIX 3.x
USG			Running a variant of System V
USGr3			Running System V.3
XENIX_22		Xenix 2.2
Linux			Linux
CRAY			running a recent version of Cray UNICOS