Support for arbitrarily large OpenCL build logs.
Merge pull request #240 from jrprice/ocl-build-log

Support for arbitrarily large OpenCL build logs
Added a warning when we encounter nested vector for loops.
Fix bug in vectorizing for loops with vector min.
Warn on pure definitions that hide other pure definitions.
Made Makefile actually test warnings.
Warn on vector loops of extent 1
Warn on nested vectorization
Add a test for the warning about parallel for loops of size one
Merge branch 'master' of github.com:halide/Halide
Added a test for issue #190
Grace period for warnings for old implicits is over
WARNING -> Warning for consistency
Made extern stages and functions work in the C backend.
Add constructor for Func wrapper from Function

Func contains all the logic for transforming a schedule, so it is useful to be
able to reconstitute a Func handle directly from a Function dug, e.g., out of
the call graph of Functions.
Fix for LLVM api change
Inline reductions optionally take the RDom that they reduce over

This lets you reference multiple RDoms inside them. Only the named one
gets captured.
Added test for bounds inference on function values.
Taught bounds inference about ceil, floor, round.

Partially fixes #199
Add visit_function helper to IRVisitor

This function applies an IRVisitor to all Exprs in a Function
definition, including update definitions, update index args,
and the extents of referenced RDoms.