Union reduction, incomplete commit.
Merge remote-tracking branch 'origin/master' into union_definition

Conflicts:
	Makefile
Added conversion of UnionReductions to Functions
Recursive splits and conversion to Functions
Bug fixes for UnionReduction
Fixed constructor of Func to initialize all data members
unstable commit
Converted split expressions so that complete dependency graph is fully exploded, ideal for merging expressions selectively.
Merge branch 'master' of https://github.com/halide/Halide
Merge branch 'master' of https://github.com/halide/Halide
Merge branch 'master' of https://github.com/halide/Halide
Merged upstream/master into union_definition
Made the static test part of the makefile more flexible for NaCl.

The following command line now runs the static tests under NaCl. Some crash:

HL_TARGET=x86-64-sse41-nacl \
STATIC_TEST_CXX=~/nacl_sdk/pepper_30/toolchain/linux_x86_newlib/x86_64-nacl/bin/g++ \
STATIC_TEST_LIBS="-Wl,--gc-sections" \
STATIC_TEST_RUNNER="/usr/local/google/home/abadams/nacl_sdk/pepper_30/tools/sel_ldr_x86_64 -B ~/nacl_sdk/pepper_30/tools/irt_core_x86_64.nexe -f" \
make test_static
Merge branch 'master' of github.com:halide/Halide
Added a julia set static test that vectorizes, parallelizes, tiles, etc.
Always use the 32-bit runtime for NaCl
Updated NaCl demo to work on arm
Merge branch 'master' of https://github.com/halide/Halide
Added new files to CMake build
Modified reorder implementation to avoid VarOrRVar::operator =