Make complaint output prettier

Make complaint output prettier

Currently complaints are not always printed with a newline.  For
example, when I run gdb on itself, I see output like:

    (gdb) set complaints 5
    (gdb) file ./gdb/gdb
    Reading symbols from ./gdb/gdb...DW_AT_low_pc 0x0 is zero for DIE at 0x437dd4 [in module /home/tromey/gdb/build/gdb/gdb]....debug_line address at offset 0x21bf9 is 0 [in module /home/tromey/gdb/build/gdb/gdb]...DW_AT_low_pc 0x0 is zero for DIE at 0x5a85dd [in module /home/tromey/gdb/build/gdb/gdb]....debug_line address at offset 0x2dc2d is 0 [in module /home/tromey/gdb/build/gdb/gdb]...DW_AT_low_pc 0x0 is zero for DIE at 0xab6033 [in module /home/tromey/gdb/build/gdb/gdb]....debug_line address at offset 0x4f683 is 0 [in module /home/tromey/gdb/build/gdb/gdb]...DW_AT_low_pc 0x0 is zero for DIE at 0x10028f0 [in module /home/tromey/gdb/build/gdb/gdb]....debug_line address at offset 0x75edf is 0 [in module /home/tromey/gdb/build/gdb/gdb]...DW_AT_low_pc 0x0 is zero for DIE at 0x1021364 [in module /home/tromey/gdb/build/gdb/gdb]....debug_line address at offset 0x76f62 is 0 [in module /home/tromey/gdb/build/gdb/gdb]...done.

That's one very long line.  I find it quite difficult to read that,
and I thought it would be better with some newlines, which is what
this patch does.  Now the output looks like:

    (gdb) file ./gdb
    Reading symbols from ./gdb...
    DW_AT_low_pc 0x0 is zero for DIE at 0x437dd4 [in module /home/tromey/gdb/build/gdb/gdb]
    .debug_line address at offset 0x21bf9 is 0 [in module /home/tromey/gdb/build/gdb/gdb]
    DW_AT_low_pc 0x0 is zero for DIE at 0x5a85dd [in module /home/tromey/gdb/build/gdb/gdb]
    .debug_line address at offset 0x2dc2d is 0 [in module /home/tromey/gdb/build/gdb/gdb]
    done.

gdb/ChangeLog
2018-10-04  Tom Tromey  <tom@tromey.com>

	PR cli/22234:
	* complaints.c: Emit \n.

gdb/testsuite/ChangeLog
2018-10-04  Tom Tromey  <tom@tromey.com>

	PR cli/22234:
	* gdb.dwarf2/dw2-stack-boundary.exp: Update expected output.
	* gdb.gdb/complaints.exp (test_short_complaints): Update expected
	output.