libast: consolidate errno ID fallbacks into error.h

In various places in libast and libcmd there are preprocessor
fallbacks like this, for systems that don't define all the commonly
used errno value IDs:

    #ifndef ENOSYS
    #define ENOSYS	EINVAL
    #endif

and many others. It is better to have these all in one place so
they are not duplicated and we don't risk inconsistencies when
adding new code.

src/lib/libast/include/error.h includes the OS's <errno.h>, so it
is the logical file to move all these fallbacks into.

Quite possibly there is no remotely current system that needs any
of these, but they won't do any harm either.

Most files already use <error.h> directly or indirectly. Four
needed new #include <error.h> directives to use the fallbacks if
needed. The libast Mamfile is updated to make those files depend on
that header.

src/lib/libast/include/error.h

@@ -39,7 +39,6 @@
 #if !defined(errno) && defined(__DYNAMIC__)
 #define errno		__DYNAMIC__(errno)
 #endif
-
 #define ERROR_debug(n)	(-(n))
 #define ERROR_exit(n)	((n)+ERROR_ERROR)
 #define ERROR_system(n)	(((n)+ERROR_ERROR)|ERROR_SYSTEM)
@@ -156,6 +155,45 @@ struct Error_info_s			/* error state			*/
 #ifndef errno
 extern int	errno;			/* system call error status	*/
 #endif
+#ifndef E2BIG
+#define E2BIG	ENOMEM
+#endif
+#ifndef EAGAIN
+#define EAGAIN	11
+#endif
+#ifndef EBADF
+#define EBADF	9
+#endif
+#ifndef EBUSY
+#define EBUSY	16
+#endif
+#ifndef EDEADLK
+#define EDEADLK	45
+#endif
+#ifndef EINTR
+#define EINTR	4
+#endif
+#ifndef EILSEQ
+#define EILSEQ	EIO
+#endif
+#ifndef EINVAL
+#define EINVAL	22
+#endif
+#ifndef ENOMEM
+#define ENOMEM	12
+#endif
+#ifndef ENOSYS
+#define ENOSYS	EINVAL
+#endif
+#ifndef EPERM
+#define EPERM	1
+#endif
+#ifndef ERANGE
+#define ERANGE	E2BIG
+#endif
+#ifndef ESPIPE
+#define ESPIPE	29
+#endif
 
 #if _BLD_ast && defined(__EXPORT__)
 #define extern		extern __EXPORT__