btrace: fix tests for 32-bit

btrace: fix tests for 32-bit

The x86-record_goto.S assembly source file does not build on 32-bit.
This breaks many tests that use this file.

Split it into x86_64-record_goto.S and i686-record_goto.S.  Luckily, we
can use either one with the same test .exp file.

It further turned out that most tests do not really need a fixed binary;
they should work pretty well with a newly-compiled C program.  The
one thing that breaks this is the heavy use of "record goto" to navigate
inside the recorded execution.

Combine step.exp, next,exp, and finish.exp into a single test step.exp
and use normal stepping and reverse-stepping commands for navigation.

testsuite/
	* gdb.btrace/next.exp: Merged into step.exp.
	* gdb.btrace/finish.exp: Merged into step.exp.
	* gdb.btrace/nexti.exp: Merged into stepi.exp.
	* gdb.btrace/step.exp: Use record_goto.c as test file.  Avoid using
	"record goto" and checking the exact replay position.
	* gdb.btrace/stepi.exp: Choose test file based on target.  Do not
	check for "Recording format" in "info record" output.
	* gdb.btrace/record_goto.exp: Choose test file based on target.
	* gdb.btrace/x86-record_goto.S: Renamed into ...
	* gdb.btrace/x86_64-record_goto.S: ... this.
	* gdb.btrace/i686-record_goto.S: New.
	* gdb.btrace/x86-tailcall.S: Renamed into ...
	* gdb.btrace/x86_64-tailcall.S: ... this.
	* gdb.btrace/i686-tailcall.S: New.
	* gdb.btrace/x86-tailcall.c: Renamed into ...
	* gdb.btrace/tailcall.c: ... this.  Split "return ++answer" into two
	separate statements.  Update test.
	* gdb.btrace/delta.exp: Use record_goto.c as test file.
	* gdb.btrace/gcore.exp: Use record_goto.c as test file.
	* gdb.btrace/nohist.exp: Use record_goto.c as test file.
	* gdb.btrace/tailcall.exp: Choose test file based on target.
	* gdb.btrace/Makefile.in: Remove next, finish, and nexti.