Remove hb-icu dependency from hb-icu-le shaper
Bug 65054 - Add configure option to enable/disable Graphite2

Add --with-graphite2.  Defaults to off.
Disable hb-old shaper

Will add proper way to enable it later.
Bug 65053 - Add configure option to enable/disable ICU support
Remove icu-config fallback for icu_le shaper

Bug 64878 - compile error with ICU but not ICU
Disable icu_le shaper

Will add a way to enable it later.
Minor
Disable UCDN if glib is available

We only want UCDN if we don't have any other Unicode provider.
I'm going to remove ICU from the list of default Unicode providers
as part of moving hb-icu into its own library.  As such, the only
providers will be UCDN and glib.