stack: More readability when adding transitions

This small refactor makes the code more readable when adding more
transition types that have left, right, up, and down variations.

It adds inline boolean functions to tell information about transition
types (avoiding long if clauses) and changes long chains of "else if
(transition_type == ...)" into switch statements. Both are only likely
to get longer as more transition types are added.

https://bugzilla.gnome.org/show_bug.cgi?id=726676
stack: Add counterparts of OVER_UP_DOWN transition

The GtkStackTransitionType enum now has OVER_DOWN_UP, OVER_LEFT_RIGHT,
and OVER_RIGHT_LEFT values to complement OVER_UP_DOWN.

https://bugzilla.gnome.org/show_bug.cgi?id=726676
GtkStack: Avoid compiler warnings

gcc warns about unhandled enum values in these switch statements,
so add an empty default: case to placate the compiler.
teststack: don't enumerate transitions manually

Thats what introspection is for.
GtkDialog: Warn about lack of transient parents

We want make it mandatory for dialogs to have transient parents,
eventually. This is a first step in that direction.
GtkColorButton: Update deprecation warnings

It is not great to have deprecation warnings point to another
deprecated function. Update them to point to the eventual
replacement.
GtkColorButton: Reduce internal use of deprecated API

Drop the blanket GDK_DISABLE_DEPRECATION_WARNINGS and avoid
deprecated API as much as possible.
queryimmodules: Localize suppressed deprecation

Drop the blanket GDK_DISABLE_DEPRECATION_WARNINGS and avoid
deprecated API as much as possible.
Drop unneeded deprecation suppression

Removing this did not produce any deprecation warnings.
GtkWidget: Mark deprecated properties as such

The ::style, ::margin-left and ::margin-right properties are all
deprecated.
GtkLevelBar: Implement new AtkValue interface

The AtkValue interface has been replaced in ATK 2.12.
Implement the new one in addition to the old one.
GtkPaned: Implement new AtkValue interface

The AtkValue interface has been replaced in ATK 2.12.
Implement the new one in addition to the old one.
GtkProgressBar: Implement new AtkValue interface

The AtkValue interface has been replaced in ATK 2.12.
Implement the new one in addition to the old one.
GtkRange: Implement new AtkValue interface

The AtkValue interface has been replaced in ATK 2.12.
Implement the new one in addition to the old one.
GtkScaleButton: Implement new AtkValue interface

The AtkValue interface has been replaced in ATK 2.12.
Implement the new one in addition to the old one.
GtkSpinButton: Implement new AtkValue interface

The AtkValue interface has been replaced in ATK 2.12.
Implement the new one in addition to the old one.
GtkDialog: Reduce a g_warning to a g_message

Otherwise, this breaks our testsuite.
a11y tests: Use the new AtkValue interface

The old interface is deprecated, and we just implemented the
new one, so lets test it.
a11y tests: Update expected output

The new AtkValue interface aways returns doubles, which causes
the range to be printed out with decimals.
a11y tests: Avoid deprecation warnings

We can't drop the index-based AtkTable methods unless we change
the output format, so just ignore the deprecations for now.