gdb: don't print trailing space after base classes in pretty format

After working on the previous patch, the formatting of the values
printed in test gdb.cp/anon-struct-with-base.exp with "print pretty on"
looks wrong to me.  I think that with "print pretty on", the "<No data
fields>" string should be on its own line.  The closing curly brace
should also be on its own line.

As an exception, when a type has absolutely nothing in it, we print
this, which seem reasonable:

    <base_no_data> = {<No data fields>},

Concretely, this patch changes this:

    $ ./gdb -nx -q --data-directory=data-directory testsuite/outputs/gdb.cp/anon-struct-with-base/anon-struct-with-base -ex "with print pretty -- p v_no_data_base_data" -ex "with print pretty -- p v_no_data_base_no_data" -batch
    $1 = {
      <base_data> = {
        a = 3
      }, <No data fields>}
    $2 = {
      <base_no_data> = {<No data fields>}, <No data fields>}

to this:

    $ ./gdb -nx -q --data-directory=data-directory testsuite/outputs/gdb.cp/anon-struct-with-base/anon-struct-with-base -ex "with print pretty -- p v_no_data_base_data" -ex "with print pretty -- p v_no_data_base_no_data" -batch
    $1 = {
      <base_data> = {
        a = 3
      },
      <No data fields>
    }
    $2 = {
      <base_no_data> = {<No data fields>},
      <No data fields>
    }

Finally, this change also gets rid of some unnecessary trailing spaces
printed after base classes.  This is not really visible for users, but
it is visible in the test changes.

Change-Id: Ia1c28c8bf2c6a8442c2cb610e06058e4dac030b9
Approved-By: Kevin Buettner <kevinb@redhat.com>