[clang] [clang] introduce constexpr step limit opt-out (PR #160440)

[Aaron Ballman via cfe-commits]

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@@ -4028,7 +4028,7 @@ Controlling implementation limits
   Sets the limit for the number of full-expressions evaluated in a single
   constant expression evaluation. This also controls the maximum size
   of array and dynamic array allocation that can be constant evaluated.
-  The default is 1048576.
+  The default is 1048576, and the limit can be disabled with `-fconstexpr-steps=0`..
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AaronBallman wrote:

```suggestion
  The default is 1048576, and the limit can be disabled with `-fconstexpr-steps=0`.
```
Removes an accidental extra full stop at the end of the sentence.

https://github.com/llvm/llvm-project/pull/160440