Fix array pretty formatter

Fix array pretty formatter

Currently, printing with array pretty formatting makes the output actually
less readable than without:

(gdb) p -array on -- {{1,2,3},{4,5,6}}
$1 =   {    {1,
    2,
    3},
      {4,
    5,
    6}}
(gdb) p -array on -array-indexes on -- {{1,2,3},{4,5,6}}
$2 =   {[0] =     {[0] = 1,
    [1] = 2,
    [2] = 3},
  [1] =     {[0] = 4,
    [1] = 5,
    [2] = 6}}

These changes now also put the first element and the array end bracket on a new
line, similar to the structure pretty formatter:

(gdb) p -array on -- {{1,2,3},{4,5,6}}
$1 = {
  {
    1,
    2,
    3
  },
  {
    4,
    5,
    6
  }
}
(gdb) p -array on -array-indexes on -- {{1,2,3},{4,5,6}}
$2 = {
  [0] = {
    [0] = 1,
    [1] = 2,
    [2] = 3
  },
  [1] = {
    [0] = 4,
    [1] = 5,
    [2] = 6
  }
}

gdb/ChangeLog:

2020-04-29  Hannes Domani  <ssbssa@yahoo.de>

	PR gdb/17320
	* ada-valprint.c (val_print_packed_array_elements): Move array
	end bracket to new line.
	(ada_val_print_string): Remove extra spaces before first array
	element.
	* c-valprint.c (c_value_print_array): Likewise.
	* m2-valprint.c (m2_print_array_contents): Likewise.
	(m2_value_print_inner): Likewise.
	* p-valprint.c (pascal_value_print_inner): Likewise.
	* valprint.c (generic_val_print_array): Likewise.
	(value_print_array_elements): Move first array element and array
	end bracket to new line.

gdb/testsuite/ChangeLog:

2020-04-29  Hannes Domani  <ssbssa@yahoo.de>

	PR gdb/17320
	* gdb.base/pretty-array.c: New test.
	* gdb.base/pretty-array.exp: New file.