refactor: remove dependency to boost.math

[Becheler]

Before submitting

• This PR targets the develop branch.
• I searched for an existing PR or issue covering the same change.
• My contribution is licensed under the Boost Software License 1.0.

Type of change

• Bug fix
• New feature or API addition
• Refactor (no behavior change)
• Documentation
• Build, CI, or tooling
• Other (specify below)

Does this PR introduce a breaking change?

• Yes (describe migration impact below)
• No

What this PR does

• remove boost.math headers and deps in CML/build.jam
• use C++11 std::hypot
• define a local pi and square root constant

Motivation

Remove dependency on Boost.Math: it's overkill here for just one STL function and 2 constants.

Testing

Checklist

• Existing tests pass (b2 in the test/ directory).
• New behavior is covered by a test, or this is a docs / build / refactor change.
• Documentation was updated if user-facing behavior changed.
• No new compiler warnings on the platforms I built against.

[github-actions]

Boost dependency footprint vs develop (auto-generated).
PR run 29569473885 vs develop run 29503421582 (5a18325250).

Header-inclusion weights (graph files pulling each direct dependency in):

Dependency	develop	PR	Δ
math	2	0	-2

Transitive Boost modules: 69 → 69 (0)

[github-actions]

Compiler-warning counts vs develop (auto-generated).
PR run 29569473921 vs develop run 29503421610 (5a18325250).

Job	Baseline	After	Delta
macos (clang, 14)	4	4	0
macos (clang, 17)	4	4	0
macos (clang, 20)	4	4	0
ubuntu (clang-19, 14)	4	4	0
ubuntu (clang-19, 17)	4	4	0
ubuntu (clang-19, 20)	4	4	0
ubuntu (clang-19, 23)	4	4	0
ubuntu (gcc-14, 14)	10	10	0
ubuntu (gcc-14, 17)	10	10	0
ubuntu (gcc-14, 20)	10	10	0
ubuntu (gcc-14, 23)	10	10	0
windows_msvc_14_3 (msvc-14.3)	971	971	0

[jeremy-murphy]

Why did you flag this as a breaking change? It doesn't seem like it to me.

[Becheler]

I don't think I flagged this PR as breaking. The breaking change is in another one, where BGL public API exposed MPL types, that can now be STL types.
Edit: oops I totally did flag it by mistake - my bad ! Friday fatigue hitting hard 😅