Document -k option as experimental
strace -k does not produce a reliable output on all supported
configurations yet, even basic strace-k.test is known to fail
on some of them.
* strace.c (usage): Document -k option as experimental.
* strace.1: Likewise.
* NEWS: Likewise.
diff --git a/strace.c b/strace.c
index 46c9d63..4154cde 100644
--- a/strace.c
+++ b/strace.c
@@ -238,7 +238,7 @@
-P path -- trace accesses to path\n\
"
#ifdef USE_LIBUNWIND
-"-k obtain stack trace between each syscall\n\
+"-k obtain stack trace between each syscall (experimental)\n\
"
#endif
/* ancient, no one should use it