LIBC (C library) include files

	ctype		character classes, conversions
	error		c_erract actions
	finfo		c_finfo data structure
	fset		FIO set/stat parameter
	knames		external kernel names
	libc		must be included by all files which use libc
	math		UNIX math functions
	spp		SPP language definitions
	stdio		UNIX standard i/o
	xnames		SPP external names
	xwhen		c_xwhen (exception handling)
	kernel		kernel constants, tables
	protect		file protection
	prtype		process types
	setjmp		non-local goto
	zfstat		FIO driver file status codes

The file "iraf.h" is referenced as <iraf.h> in IRAF C source files, and is used
to load all other IRAF/LIBC C header files via "#define import_XXX" defines in
these files.  In order for the C compiler to find <iraf.h>, one should either
[1] add the directory $hlib/libc to the list of directories to be searched by
the C compiler for include files, or [2] make a link to, or copy of,
libc/iraf.h in the system directory /usr/include.
