properties can't be set until Validate-time (eg, Method.IsGetter),
but it's annoying for every potential user of those properties to
have to make sure it has Validated the generatable first. So now
we add an explicit Validate() step after everything is loaded but
before anything is Generated, so that at Generation time,
everything can be assumed to have been Validated.
* generator/IGeneratable.cs: add "bool Validate()"
* generator/CodeGenerator.cs (Main): after loading all of the
generatables, DeAlias the SymbolTable, Validate() all the
generatables, and discard any invalid ones.
* generator/*.cs: Implement Validate() trivially in generatables
that didn't implement it before. Move Validate() calls from
Generate() to Validate(). Remove non-hierarchical Validate()
calls.
* generator/SymbolTable.cs: GPtrArray is IntPtr, not IntPtr[]
svn path=/trunk/gtk-sharp/; revision=48046
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