use `object.__eq__`(default object identity comparison) as default
implementation of same_as. This should be OK since `EqualOp` and
`NotEqualOp` are pure Python object, `object.__eq__` is sufficient.

* [PYTHON] Improve equal sugar

* fix comment

* [ARITH] More caninical simplfy

* [DEBUG] Use HalideIR with trace logging

* [FIX] Fix target warning

* [FIX] Deduplicate options

* Fix

* Fix

* [CODEGEN] Allow link additional module

* fix py3

* add register back

* [CODEGEN] Force not inline compute core for better debug

* also support llvm4

* [TVM] Introduce target generic dispatch system

* fix target warning

* [CODEGEN] Detect broadcast(cast(x)) pattern in FMA

* [CODEGEN] Improve

* [CODEGEN] Fix

* Add same_as to NodeBase

1. Most class inherited from NodeBase(Schedule, Stage, etc) still have
the convenience of using '==' for object identity. And this is the right
behavior for non-Expr classes.
2. subclasses of ExprOp now create EQ expression when '==' is used.

`__nonzero__` and `__bool__` in EQ and NE is a comprise that in some cases
object identity semantics is still useful, like in unit test. For instance:
````
assert a == b
````

"a == b" will create EQ expression, assert then calls `__nonzero__` of the
result expression. `Expr.__nonzero__` throws exception since it prohibits
evaluating IR expression.

More complex case like:
````
assert a in b # b is dict
````

it will call `__eq__` on a and all keys of b, then `__bool__` on the result
expression. This could not easily be done by same_as.

* Retain __hash__ from NodeBase in Python3

* added support for rocm gpu autodetect

* changed type casting from old style to static_cast

* fixed code to generate gfx specific code object

* fixed namespaces

* add masahi to contributors

* enable rocm target in topi tests

also improve comment and unit test

* [RUNTIME] Enable ext_dev type for quick plugin of device

* [TEST] Update testcase to cover all computation

* [PASS] copy intrin

* update comment thanks to derisavi

* Case-sensitive CMake module for OpenCL

Case-sensitive CMake module for OpenCL, see https://github.com/Kitware/CMake/blob/master/Modules/FindOpenCL.cmake .

* fix in case Metal locates OpenCL as well

fix in case Metal locates OpenCL as well

* [ARITH] Improve detect linear equation

* fix doc

* add argmax argmin

* remove coder saver

* conv2d tweaked for better end-to-end performance

* syntax changed

* conv2d layout change bug fixed

* remove debug msg

* misaligned error fixed

* [TOPI] Add left_shift, right_shift, clip, cast

* [TOPI] Add test

* [TOPI] Fix

* [LANG] Support for Bitwise Operation

* Add test