strace.c: support simultaneous usage of -r and -t options

strace.c: support simultaneous usage of -r and -t options

* strace.c (init): Do not set tflag when rflag is set.
(printleader): Handle rflag and tflag separately.
* strace.1.in (.SH OPTIONS): Add a note about differences between
the monotonic clock time  and the wall clock time.
* tests/options-syntax.test: Remove the check for
"-tt has no effect with -r" warning.
* NEWS: Mention this.

Suggested-by: Josh Triplett <josh@freedesktop.org>
Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=466195