trace: allow PRI*64 at beginning and ending of format string

trace: allow PRI*64 at beginning and ending of format string

The tracetool parser only picks up PRI*64 and other format string macros
when enclosed between double quoted strings.  Lift this restriction by
extracting everything after the closing ')' as the format string:

  cpu_set_apic_base(uint64_t val) "%016"PRIx64
                                  ^^        ^^

One trick here: it turns out that backslashes in the format string like
"\n" were being interpreted by echo(1).  Fix this by using the POSIX
printf(1) command instead.  Although it normally does not make sense to
include backslashes in trace event format strings, an injected newline
causes tracetool to emit a broken header file and I want to eliminate
cases where broken output is emitted, even if the input was bad.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>