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_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:

GWINSZ_IN_SYS_IOCTL	need to include <sys/ioctl.h> for TIOCGWINSZ
HAVE_GETPW_DECLS	the getpw* functions are declared in <pwd.h> and cannot
			be redeclared without compiler errors
HAVE_STRCASECMP		the strcasecmp and strncasecmp functions are available

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
SunOS4			Running SunOS 4.x