Change minimum compiler versions for <charconv> interop

doc/decimal/config.adoc

@@ -45,4 +45,4 @@ This flag increases the performance of the basis operations (e.g. add, sub, mul,
 
 - `BOOST_DECIMAL_HAS_STD_CHARCONV`: This macro is defined if header `<charconv>` exists and the language standard used is >= C++17
  * We only need the structs and enums out of the header so we are not concerned with being overly restrictive about the feature test macros.
- Implementations of integer `std::from_chars` and `std::to_chars` existed far before the floating points were completed to allow the feature test macro to be properly set.
+  ** Known compilers that support this lighter requirement are: GCC >= 10, Clang >= 13, and MSVC >= 14.2

include/boost/decimal/detail/config.hpp

@@ -314,10 +314,14 @@ typedef unsigned __int128 uint128_t;
 
 #if __cplusplus >= 201703L
 # if __has_include(<charconv>)
-# ifndef BOOST_DECIMAL_BUILD_MODULE
-# include <charconv>
+ // We don't need all of charconv, just: std::to_chars_result, std::from_chars_result, and std::chars_format
+ // These compilers and versions give us what we need
+# if (defined(__clang_major__) && __clang_major__ >= 13) || (defined(__GNUC__) && __GNUC__ >= 10) || defined(_MSC_VER)
+# ifndef BOOST_DECIMAL_BUILD_MODULE
+# include <charconv>
+# endif
+# define BOOST_DECIMAL_HAS_STD_CHARCONV
 # endif
-# define BOOST_DECIMAL_HAS_STD_CHARCONV
 # endif
 #endif