- [boost] add new mirror

[SSE4]

• [boost] add new mirror

Specify library name and version: boost/all

This is also a good place to share with all of us why you are submitting this PR (specially if it is a new addition to ConanCenter): is it a dependency of other libraries you want to package? Are you the author of the library? Thanks!

see #5197 (comment)

---

• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the
  conan-center hook activated.

[ghost]

I detected other pull requests that are modifying boost/all recipe:

• [boost] For Visual Studio, pass some values of settings.compiler.toolset to B2 #5119
• Fix for Boost build failure on Windows when not able to find MSVC toolset #5099
• boost: header only boost::system #5051
• boost: use clang-win toolset when compiler=Visual Studio and compiler.toolset=ClangCL #4749
• [boost] b2 user-config.jam needs CXX binary to be quoted as path may contain spaces #4149
• Boost/1.72.0/mpi #3959
• boost: patch serialization sources #3918

This message is automatically generated by https://github.com/ericLemanissier/conan-center-conflicting-prs so don't hesitate to report issues/improvements there.

[Croydon]

Remove Bintray already? I don't see the point of leaving it there for another 2 weeks just to remove it then

[SSE4]

I think more mirrors is harmless, but increases reliability, in case of boostorg.jfrog.io is unreachable for whatever reason, dl.bintray.com could be used as a fallback

[conan-center-bot]

All green in build 3 (baf69ba144acc82d9084f7107785ce7a391c6828):

• boost/1.69.0@:
  All packages built successfully! (All logs)

• boost/1.70.0@:
  All packages built successfully! (All logs)

• boost/1.71.0@:
  All packages built successfully! (All logs)

• boost/1.72.0@:
  All packages built successfully! (All logs)

• boost/1.75.0@:
  All packages built successfully! (All logs)

• boost/1.73.0@:
  All packages built successfully! (All logs)

• boost/1.74.0@:
  All packages built successfully! (All logs)