Clean up "Reading symbols" output

Clean up "Reading symbols" output

This patch is another attempt to fix PR cli/19551.  Unlike my previous
attempt, it doesn't print progress.  Instead, it just changes some
messages and adds newlines to make the output a bit nicer.

It also removes the "done." text that was previously emitted.  The
idea here is that it is obvious when gdb is done reading debug info,
as it starts then doing something else; and that while this message
did not provide much benefit to users, it did make it harder to make
the output clean.

After this change the output from "./gdb -iex 'set complaint 1' -nx ./gdb"
reads:

    Reading symbols from ./gdb...
    .debug_ranges entry has start address of zero [in module /home/tromey/gdb/build/gdb/gdb]
    DW_AT_low_pc 0x0 is zero for DIE at 0x17116c1 [in module /home/tromey/gdb/build/gdb/gdb]
    .debug_line address at offset 0xa22f5 is 0 [in module /home/tromey/gdb/build/gdb/gdb]
    During symbol reading, unsupported tag: 'DW_TAG_unspecified_type'.
    During symbol reading, const value length mismatch for 'std::ratio<1, 1000000000>::num', got 8, expected 0.

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

	PR cli/19551:
	* symfile.c (symbol_file_add_with_addrs): Update output.
	* psymtab.c (require_partial_symbols): Update output.

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

	PR cli/19551:
	* lib/mi-support.exp (mi_gdb_file_cmd): Update.
	* lib/gdb.exp (gdb_file_cmd): Update.
	* gdb.stabs/weird.exp (print_weird_var): Update.
	* gdb.server/solib-list.exp: Update.
	* gdb.multi/remove-inferiors.exp (test_remove_inferiors): Update.
	* gdb.mi/mi-cli.exp: Update.
	* gdb.linespec/linespec.exp: Update.
	* gdb.dwarf2/dw2-stack-boundary.exp: Update.
	* gdb.dwarf2/dw2-objfile-overlap.exp: Update.
	* gdb.cp/cp-relocate.exp: Update.
	* gdb.base/sym-file.exp: Update.
	* gdb.base/relocate.exp: Update.
	* gdb.base/readnever.exp: Update.
	* gdb.base/print-symbol-loading.exp (test_load_core): Update.
	* gdb.base/kill-detach-inferiors-cmd.exp: Update.
	* gdb.base/dbx.exp (gdb_file_cmd): Update.
	* gdb.base/code_elim.exp: Update.
	* gdb.base/break-unload-file.exp (test_break): Update.
	* gdb.base/break-interp.exp (test_attach_gdb): Update.
	* gdb.base/break-idempotent.exp (force_breakpoint_re_set):
	Update.
	* gdb.base/attach.exp (do_attach_tests): Update.
	* gdb.base/sepdebug.exp: Update.
	* gdb.python/py-section-script.exp: Update.