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/strace.c b/strace.c
index bda091e..66dee5f 100644
--- a/strace.c
+++ b/strace.c
@@ -58,7 +58,7 @@
 #  define my_tkill(tid, sig) kill((tid), (sig))
 # endif
 
-#if defined(IA64) && defined(LINUX)
+#if defined(IA64)
 # include <asm/ptrace_offsets.h>
 #endif