Prep for breaking change in #562

purpose

This release is going to seed a branch to track this state for those that do not wish to adopt the breaking changes in #562

What's Changed

• Remove static from observe_on_run_loop by @lebdron in #449
• group_by support DurationSelector by @diorcety in #447
• adding test for nocompare observe_on by @kirkshoop in #448
• fix blocking_observable::subscribe by @kirkshoop in #453
• fix #390 by @yatli in #454
• Fix doc target missing declarations errors by @gsauthof in #464
• Update ide build to Visual Studio 2017 by @zwcloud in #466
• Add support for compiling rxcpp with -fno-exceptions by @iam in #456
• fixes for replay and moved-from container not being empty by @kirkshoop in #467
• Small fixes. by @besser82 in #476
• README: fix cmake generation snippet for clang/linux by @iam in #479
• cmake: Fix 'make' generator targets by @iam in #480
• rxcpp: Fix data race in composite_subscription by @iam in #481
• removing a pedantic compile warning by @thorstink in #488
• operators: Add ref_count(other) operator overload. by @iam in #485
• Fix data race in run loop usage by @lebdron in #486
• Fix synchronize lock and recursion data race by @lebdron in #493
• dox: fix dead rxmarbles link by @NeroBurner in #495
• Fix address sanitizer issue in new_worker (rx-newthread.hpp) by @luckychess in #497
• removed constexpr to support older VC compilers. by @joe2018Outlookcom in #504
• make find_package(rxcpp CONFIG) work through exporting TARGETS by @Exctues in #509
• Add instructions to install RxCpp using vcpkg by @vicroms in #510
• Observable forward declaration header by @lebdron in #511
• Changed values_from template parameter to not cast. by @tinkerbeast in #521
• add this to captures due to c++20 deprecation by @kirkshoop in #527
• Corrected rare deadlock condition on observable.as_blocking().subscribe() by @quetzalcoatl in #543
• Fixed build interface include directories for CMake projects by @spreagtha in #536
• Fix std::result_of removed in C++20 by @Asaaj in #551
• Include in rx-includes.hpp by @kamleshbhalui in #547
• [FixCrash][Perfomance]Remove unnecessary "this" capture for subjects to prevent crashes for stack subjects variables. by @victimsnino in #561

Full Changelog: v4.1.0...v4.1.1