Reduce bss usage and speed up string printing

Reduce bss usage and speed up string printing

   text	   data	    bss	    dec	    hex	filename
 237913	    660	  49284	 287857	  46471	strace.before
 237973	    660	  28772	 267405	  4148d	strace

This reduces L1 D-cache pressure a bit: instead of dirtying
20k of bss, we will reuse already dirty stack area.

* util.c (printpathn): Use on-stack buffers instead of static ones.
Saves 5*MAXPATHLEN in bss.
(printstr): Use tprints() instead of tprintf("%s") when printing
formatted string. May be a bit faster, depending on libc.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>