[RFC] optabs and tree-codes for vector operations

[Devang Patel]

I am preparing following patches to complete vector conditional 
operations support.

	[PATCH] Add VEC_COND_EXPR node

	[PATCH] AV - Use distance vector

	[PATCH] Add vcond_gen_code optab and expand VEC_COND_EXPR

	[PATCH] RS6000 : Add support for vector conditionals

	[PATCH] Update if-conversion for AV

	[PATCH] Vectorize if-converted loop

I'll address broken altivec.md issue (vec_select and vec_merge mess) 
after this.
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Devang