Move custom features to its own file we can import from other projects.

build.jam

@@ -7,9 +7,8 @@ require-b2 5.2 ;
 
 import-search /boost/predef/tools/check ;
 
-import feature ;
-import os ;
 import predef ;
+import boost-context-features ;
 
 constant boost_dependencies :
     /boost/assert//boost_assert
@@ -29,59 +28,6 @@ project /boost/context
         [ predef.architecture ]
     ;
 
-feature.feature segmented-stacks : on : optional propagated composite ;
-feature.compose <segmented-stacks>on : <define>BOOST_USE_SEGMENTED_STACKS ;
-
-feature.feature htm : tsx : optional propagated composite ;
-feature.compose <htm>tsx : <define>BOOST_USE_TSX ;
-
-feature.feature valgrind : on : optional propagated composite ;
-feature.compose <valgrind>on : <define>BOOST_USE_VALGRIND ;
-
-local rule default_binary_format ( )
-{
-    local tmp = elf ;
-    if [ os.name ] = "NT" { tmp = pe ; }
-    else if [ os.name ] = "CYGWIN" { tmp = pe ; }
-    else if [ os.name ] = "AIX" { tmp = xcoff ; }
-    else if [ os.name ] = "MACOSX" { tmp = mach-o ; }
-    return $(tmp) ;
-}
-
-feature.feature binary-format
-   : elf
-     mach-o
-     pe
-     xcoff
-   : propagated
-   ;
-feature.set-default binary-format : [ default_binary_format ] ;
-
-local rule default_abi ( )
-{
-    local tmp = sysv ;
-    if [ os.name ] = "NT" { tmp = ms ; }
-    else if [ os.name ] = "CYGWIN" { tmp = ms ; }
-    else if [ os.platform ] in "ARM" "ARM64" { tmp = aapcs ; }
-    else if [ os.platform ] = "MIPS32" { tmp = o32 ; }
-    else if [ os.platform ] = "MIPS64" { tmp = n64 ; }
-    return $(tmp) ;
-}
-
-feature.feature abi
-   : aapcs
-     eabi
-     ms
-     n32
-     n64
-     o32
-     o64
-     sysv
-     x32
-   : propagated
-   ;
-feature.set-default abi : [ default_abi ] ;
-
 explicit
     [ alias boost_context : build//boost_context ]
     [ alias all : boost_context test ]