Revert "Remove single header"

This reverts commit f24d1ca5df.

tools/single-header.bat

@@ -0,0 +1 @@
+python2.7 tools\single-header.py > include\boost\mp11_single.hpp

tools/single-header.py

@@ -0,0 +1,54 @@
+
+# Copyright 2017 Peter Dimov.
+#
+# Distributed under the Boost Software License, Version 1.0.
+#
+# See accompanying file LICENSE_1_0.txt or copy at
+# http://www.boost.org/LICENSE_1_0.txt
+
+import os.path
+import re
+import sys
+
+included = []
+
+def scan_header( prefix, dir, fn ):
+
+	path = os.path.join( prefix, dir, fn )
+
+	if path in included:
+
+		return
+
+	included.append( path )
+
+	with open( path, 'r' ) as header:
+	
+		for line in header:
+		
+			m = re.match( '[ \t]*#[ \t]*include[ \t]*(["<])([^">]*)[">]', line )
+			
+			r = False
+
+			if m:
+
+				h = m.group( 2 )
+
+				hfn1 = os.path.join( prefix, h )
+				hfn2 = os.path.join( prefix, dir, h )
+
+				if m.group( 1 ) == '"' and os.path.exists( hfn2 ):
+
+					scan_header( prefix, os.path.join( dir, os.path.dirname( hfn2 ) ), os.path.basename( hfn2 ) )
+					r = True
+
+				elif os.path.exists( hfn1 ):
+
+					scan_header( prefix, os.path.dirname( h ), os.path.basename( h ) )
+					r = True
+
+			if not r:
+
+				sys.stdout.write( line )
+
+scan_header( 'include', 'boost', 'mp11.hpp' )