Simplify gdb.reverse/until-reverse.c

Simplify gdb.reverse/until-reverse.c

Nowadays, functions fprintf, printf and malloc are executed in
gdb.reverse/until-reverse.c, so that it takes much time to record
instructions inside them.  This may cause timeout, and we had several
fixes to bump the timeout,

 https://sourceware.org/ml/gdb-patches/2012-02/msg00038.html
 https://sourceware.org/ml/gdb-patches/2015-08/msg00186.html

also I still see this on arm-linux,

 continue
 Continuing.
 Do you want to auto delete previous execution log entries when record/replay buffer becomes full (record full stop-at-limit)?([y] or n) n
 Process record: stopped by user.

 Program stopped.
 0xf77021e6 in __linkin_atfork (newp=0xf7751748 <atfork_mem>) at ../nptl/sysdeps/unix/sysv/linux/register-atfork.c:117
 117     ../nptl/sysdeps/unix/sysv/linux/register-atfork.c: No such file or directory.
 (gdb) FAIL: gdb.reverse/until-precsave.exp: run to end of main (got interactive prompt)

however, I can't figure out how these functions (fprintf, printf and
malloc) are related to the test itself.  marker1 is a function from
shared library too so we don't need these complicated libc functions
at all.  IMO, recording the instructions in these libc functions has
nothing to do with the test itself except slow down the test.  This
patch is to remove the usage of fprintf and printf, and also move
malloc to a dead code path.

gdb/testsuite:

2016-03-30  Yao Qi  <yao.qi@linaro.org>

	* gdb.reverse/until-precsave.exp: Match function name only.
	* gdb.reverse/until-reverse.c (main): Don't call fprintf nor printf.
	Move malloc to a condition block.
	* gdb.reverse/until-reverse.exp: Match function name only.