Follow the example of strace.1 and put the description of -k option
into the output format group.
* strace.c (usage): Move description of -k option to the output
format group.
Output format:\n\
-a column alignment COLUMN for printing syscall results (default %d)\n\
-i print instruction pointer at time of syscall\n\
+"
+#ifdef USE_LIBUNWIND
+"\
+ -k obtain stack trace between each syscall (experimental)\n\
+"
+#endif
+"\
-o file send trace output to FILE instead of stderr\n\
-q suppress messages about attaching, detaching, etc.\n\
-r print relative timestamp\n\
-h print help message\n\
-V print version\n\
"
-#ifdef USE_LIBUNWIND
-" -k obtain stack trace between each syscall (experimental)\n\
-"
-#endif
/* ancient, no one should use it
-F -- attempt to follow vforks (deprecated, use -f)\n\
*/