Cleanup after non-Linux code removal.

Conditions such as defined(LINUX) are always true now,
defined(FREEBSD) etc are always false.
When if directive has them as subexpressions, it can be simplified.
Another trivial changes here are fixes for directive indentation.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/desc.c b/desc.c
index 2d5ac5d..be327eb 100644
--- a/desc.c
+++ b/desc.c
@@ -465,13 +465,13 @@
 	return do_dup2(tcp, 2);
 }
 
-#if defined(ALPHA) || defined(FREEBSD) || defined(SUNOS4)
+#if defined(ALPHA)
 int
 sys_getdtablesize(struct tcb *tcp)
 {
 	return 0;
 }
-#endif /* ALPHA || FREEBSD || SUNOS4 */
+#endif
 
 static int
 decode_select(struct tcb *tcp, long *args, enum bitness_t bitness)