1.11.1-rc4

• Added GitHub Actions CI on macOS, Linux, and Windows with Clang, GCC, MinGW, and Visual C++;
• Added recognition for Visual C++ 18.x in stlsoft/stlsoft.h;
• Fixed winstl::codepage_sequence::data() missing return statement;
• Fixed signed/unsigned comparison warning in winstl_C_printf_debug_string();
• Aligned Clang 64-bit sized types with GCC to use long long instead of __INT64_TYPE__ to avoid overload collision on Linux LP64;
• Added overflow checks in allocator allocate() to prevent wrapping and fix GCC -Walloc-size-larger-than= warnings;
• Fixed potential unsigned underflow in unixstl::pid_sequence when empty;
• Added MinGW compatibility guards in winstl/util/struct_comparers.hpp;
• Aligned test and example runner scripts across shell and Windows command counterparts;
• Added --unit-only and --component-only flags to unit test runners;
• Added run_all_examples scripts with --skip-interactive support;