See https://github.com/llvm/llvm-project/pull/147168 for more info.

These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

This patch adds the erfc op to the math dialect. It also does lowering
of the math.erfc op to libm calls. There is also a f32 polynomial
approximation for the function based on

https://stackoverflow.com/questions/35966695/vectorizable-implementation-of-complementary-error-function-erfcf
This is in turn based on
M. M. Shepherd and J. G. Laframboise, "Chebyshev Approximation of
(1+2x)exp(x^2)erfc x in 0 <= x < INF", Mathematics of Computation, Vol.
36, No. 153, January 1981, pp. 249-253.
The code has a ULP error less than 3, which was tested, and MLIR test
values were verified against the C implementation.

`let constructor` is deprecated since the table gen backend emits most
of the glue logic to build a pass. This PR retires the td method for
most (I need another pass) passes in the Conversion directory.

Co-authored-by: Ivan R. Ivanov <ivanov.i.aa@m.titech.ac.jp>

This fixes the following failure when doing a clean build (in particular
no .ninja* lying around) of lib/libMLIRMathToLibm.a only:
```
In file included from llvm/include/llvm/IR/Module.h:22,
                 from mlir/include/mlir/Dialect/LLVMIR/LLVMDialect.h:37,
                 from mlir/lib/Conversion/MathToLibm/MathToLibm.cpp:13
llvm/include/llvm/IR/Attributes.h:90:14: fatal error: llvm/IR/Attributes.inc: No such file or directory
```

1. Expand legal op list in `legalizeToF32`
2. add legalization support for `math::rsqrtOp` in `mathToLibm`.

This PR adds support for lowering the following Math operations to
`libm` calls:
* `math.absf` -> `fabsf, fabs`
* `math.exp` -> `expf, exp`
* `math.exp2` -> `exp2f, exp2`
* `math.fma` -> `fmaf, fma`
* `math.log` -> `logf, log`
* `math.log2` -> `log2f, log2`
* `math.log10` -> `log10f, log10`
* `math.powf` -> `powf, pow`
* `math.sqrt` -> `sqrtf, sqrt`

These operations are direct members of `libm`, and do not seem to
require any special manipulations on their operands.

Signed-Off By: Vivek Khandelwal <vivekkhandelwal1424@gmail.com>

Make it so that PDL in pattern rewrites can be optionally disabled.

PDL is still enabled by default and not optional bazel. So this should
be a NOP for most folks, while enabling other to disable.

This only works with tests disabled. With tests enabled this still
compiles but tests fail as there is no lit config to disable tests that
depend on PDL rewrites yet.