This has several fixes that Glom needs.

* glom/libglom/data_structure/glomconversions.[h|cc]:
  Add a get_text_for_gda_value() overload that takes a locale name,
  so we do not need to just use the current locale.
* glom/report_builder.cc: Use the new overload instead of ignoring
  the provided locale for this.
* tests/test_selfhosting_new_then_report.cc
* tests/test_selfhosting_new_then_report_summary.cc:
  Pass the en_US.UTF-8 locale name to the ReportBuilder constructor,
  instead of depending on the system's current locale,
  so this tests can pass regardless of the current locale.

This lets us use it in tests.

* glom/libglom/data_structure/tableinfo.h(): Add operator==()
  and operator!=().
* glom/libglom/document/document.cc(): set_tables(): Check for a
  change before re-setting this and marking
  the document as modified.

* glom/mode_data/datawidget/dialog_choose_id.cc:
  See Glom bug #660347 and gtkmm bug #605728 .

Some file had this typo and was probably then copied into new files.

* examples/example_smallbusiness.glom: Add a string default
  value, so we can test it. There are already some numeric
  default values.
* Makefile_tests.am:
* tests/test_selfhosting_new_from_example_defaultvalues.cc:
  Check some default values.

* glom/libglom/db_utils.cc: Previously libgda got this wrong,
  but it has been fixed for a while now and we depend on newer
  versions.

This would have been broken since replacing GtkTable with GtkGrid.