Replace hard-coded host$bin paths by IRAFPATH

[olebole]

The function irafpath() resolves the full path for a given IRAF file. The file is searched in the following directories:

• host$bin(arch): system build executables and libraries

• host$hlib: include files and shell scripts

• iraf$bin(arch): IRAF executables and libraries

• iraf$lib: IRAF include files and libraries (links)

While iraf$bin(arch) is created from IRAFARCH, host$bin(arch) is hardcoded by defines like #ifdef __x86_64__. This has two disadvantages: First, it fixes the architecture names in the executable, and second it requires a source change for every new arch. And it does not allow to have only arch-independent directory names, as it is used f.e. in Debian.

This patch unifies the handling architectures in irafpath(). This continues the path started with #117.

The code in question goes back to the first recorded IRAF version 2.8:

iraf/unix/os/irafpath.c

Lines 68 to 101 in 155505b

	/* Look first in HBIN.
	*/
	strcpy (pathname, (char *)hostdir);
	strcat (pathname, "bin.");
	#ifdef mc68010
	strcat (pathname, "mc68010");
	#else
	#ifdef mc68020
	strcat (pathname, "mc68020");
	#else
	#ifdef mc68030
	strcat (pathname, "mc68030");
	#else
	#ifdef sparc
	strcat (pathname, "sparc");
	#else
	#ifdef i386
	strcat (pathname, "i386");
	#else
	#ifdef vax
	strcat (pathname, "vax");
	#endif
	#ifdef CONVEX
	strcat (pathname, "convex");
	#endif
	#endif
	#endif
	#endif
	#endif
	#endif
	strcat (pathname, "/");
	strcat (pathname, fname);
	if (access (pathname, 0) == 0)
	return (pathname);

[olebole]

Cross-check for arch-independent directory names on Debian: all build logs