[GSoC] Addition of ISL AST generation to Graphite

[Roman Gareev]

These patches add ISL AST generation to graphite, which can be chosen
by the fgraphite-code-generator=[isl|cloog] switch. The first patch
makes initial renaming of gloog and gloog_error to
graphite_regenerate_ast_cloog and graphite_regenerate_error,
respectively. The second one adds new files with generation of ISL
AST, new switch, new testcase that checks that the dump is generated.

Is it fine for trunk?

P.S. My copyright assignment has been already processed.

--
                                   Cheers, Roman Gareev

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