target: add support for 64bit data in mem2array and array2mem

- Added support for reading and writing 64-bit data items
  using TCL commands "mem2array" and "array2mem". Until now,
  data items only up to 32 bits were supportd.

- Cleaned up functions target_array2mem() and
  target_mem2array(), especially data types of variables
  and variable declarations (scope).

Change-Id: Ia0ba427804f8fd8d7568f12714ab36984d6d5e24
Signed-off-by: Jan Matyas <matyas@codasip.com>
Reviewed-on: http://openocd.zylin.com/6286
Tested-by: jenkins
Reviewed-by: Marc Schink <dev@zapb.de>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

doc/openocd.texi

@@ -4821,8 +4821,8 @@ They are not otherwise documented here.
 @deffn {Command} {$target_name array2mem} arrayname width address count
 @deffnx {Command} {$target_name mem2array} arrayname width address count
 These provide an efficient script-oriented interface to memory.
-The @code{array2mem} primitive writes bytes, halfwords, or words;
-while @code{mem2array} reads them.
+The @code{array2mem} primitive writes bytes, halfwords, words
+or double-words; while @code{mem2array} reads them.
 In both cases, the TCL side uses an array, and
 the target side uses raw memory.
 
@@ -4835,7 +4835,7 @@ and neither store nor return those values.
 
 @itemize
 @item @var{arrayname} ... is the name of an array variable
-@item @var{width} ... is 8/16/32 - indicating the memory access size
+@item @var{width} ... is 8/16/32/64 - indicating the memory access size
 @item @var{address} ... is the target memory address
 @item @var{count} ... is the number of elements to process
 @end itemize