Enable std::array overloads for boost::asio on clang:

* Remove Boost config option from beast config.
* Define from compiler, or let Boost figure out itself.

SConstruct

@@ -265,6 +265,7 @@ def config_env(toolchain, variant, env):
 
         if toolchain == 'clang':
             env.Append(CCFLAGS=['-Wno-redeclared-class-member'])
+            env.Append(CPPDEFINES=['BOOST_ASIO_HAS_STD_ARRAY'])
 
         env.Append(CXXFLAGS=[
             '-frtti',

src/beast/beast/Config.h

@@ -26,9 +26,6 @@
 
 // VFALCO NOTE this is analogous to <boost/config.hpp>
 
-// Assert to boost that we always have std::array support
-#define BOOST_ASIO_HAS_STD_ARRAY 1
-
 #if !defined(BEAST_COMPILER_CONFIG) && !defined(BEAST_NO_COMPILER_CONFIG) && !defined(BEAST_NO_CONFIG)
 #include <beast/config/SelectCompilerConfig.h>
 #endif