Move traceframe checking out of traceframe generation

This patch moves traceframe checking code out of traceframe generation,
so that we can generation traceframe once, and do the checking in multiple
times (with target remote, tfile and ctf respectively).  This is a
pure refactor, not functional changes in unavailable.exp.

gdb/testsuite:

2014-05-05  Yao Qi  <yao@codesourcery.com>

	* gdb.trace/unavailable.exp (gdb_collect_args_test): Move some
	code to ...
	(gdb_collect_args_test_1): ... it.  New proc.
	(gdb_collect_locals_test): Move some code to ...
	(gdb_collect_locals_test_1): ... it.  New proc.
	(gdb_unavailable_registers_test): Move some code to ...
	(gdb_unavailable_registers_test_1): ... it.  New proc.
	(gdb_unavailable_floats): Move some code to ...
	(gdb_unavailable_floats_1): ... it.  New proc.
Show new created display

When I run refactored unavailable.exp, I find
command display behaves a little different on live inferior and on
examining traceframes.  In live inferior, when command "display argc"
is typed, the value of "argc" is shown.

(gdb) display argc
1: argc = 1 '\001'

however, on tfile target, when command "display argc" is typed, the
value of "argc" is not shown.

(gdb) tfind
Found trace frame 0, tracepoint 1
    at ../../../../git/gdb/testsuite/gdb.trace/unavailable.cc:198
198       i =  (int) argc + argi + argf + argd + argstruct.memberi + argarray[1];
(gdb) display argc

I also notice that on "core" target, the value of "argc" isn't shown
either.  This difference is caused by the code below in printcmd.c:display_command,

      if (from_tty && target_has_execution)
        do_one_display (new);

Looks the value of each display is shown if the target has execution.
Source code archaeology doesn't tell much about this requirement.
However, if we type command "display" then on "core" or "tfile"
target, the value of "argc" is still displayed,

for "core" target,
(gdb) display argc
(gdb) display
1: argc = 1 '\001'

for "tfile" target,
(gdb) display argc
(gdb) display
1: argc = <unavailable>

I feel that it is not necessary to have such "target has execution"
requirement to show the value of new created display.  Auto-display is
a feature to show the value of expression frequently, has nothing to
do with whether target has execution or not.  On the other hand, GDB
has the requirement for new created display, but command "display" can
still show them, this is an inconsistency, which should be fixed.

This patch is to remove the checking to target_has_execution from the
condition.

gdb:

2014-05-05  Yao Qi  <yao@codesourcery.com>

	* printcmd.c (display_command): Remove the check to
	target_has_execution.
Partially available/unavailable data in requested range

In gdb.trace/unavailable.exp, an action is defined to collect
struct_b.struct_a.array[2] and struct_b.struct_a.array[100],

struct StructB
{
  int d, ef;
  StructA struct_a;
  int s:1;
  static StructA static_struct_a;
  const char *string;
};

and the other files are not collected.

When GDB examine traceframe collected by the action, "struct_b" is
unavailable completely, which is wrong.

(gdb) p struct_b
$1 = <unavailable>

When GDB reads 'struct_b', it will request to read memory at struct_b's address
of length LEN.  Since struct_b.d is not collected, no 'M' block
includes the first part of the desired range, so tfile_xfer_partial returns
TARGET_XFER_UNAVAILABLE and GDB thinks the whole requested range is unavailable.

In order to fix this problem, in the iteration to 'M' blocks, we record the
lowest address of blocks within the request range.  If it has, the requested
range isn't unavailable completely.  This applies to ctf too.  With this patch
applied, the result looks good and fails in unavailable.exp is fixed.

(gdb) p struct_b
$1 = {d = <unavailable>, ef = <unavailable>, struct_a = {a = <unavailable>, b = <unavailable>, array = {<unavailable>,
<unavailable>, -1431655766, <unavailable> <repeats 97 times>, -1431655766, <unavailable> <repeats 9899 times>}, ptr = <unavailable>, bitfield = <unavailable>}, s = <unavailable>,   static static_struct_a = {a = <unavailable>, b = <unavailable>, array = {<unavailable> <repeats 10000 times>}, ptr = <unavailable>,
bitfield = <unavailable>}, string = <unavailable>}

gdb:

2014-05-05  Yao Qi  <yao@codesourcery.com>
	    Pedro Alves  <palves@redhat.com>

	* tracefile-tfile.c (tfile_xfer_partial): Record the lowest
	address of blocks that intersects the requested range.  Trim
	LEN up to LOW_ADDR_AVAILABLE if read from executable read-only
	sections.
	* ctf.c (ctf_xfer_partial): Likewise.

gdb/testsuite:

2014-05-05  Yao Qi  <yao@codesourcery.com>

	* gdb.trace/unavailable.exp (gdb_collect_args_test): Save
	traceframes into tfile and ctf trace files.  Read data from
	trace file and test collected data.
	(gdb_collect_locals_test): Likewise.
	(gdb_unavailable_registers_test): Likewise.
	(gdb_unavailable_floats): Likewise.
	(gdb_collect_globals_test): Likewise.
	(top-level): Append "ctf" to trace_file_targets if GDB
	supports.