revert loading sfmt by default

basis/random/backend/authors.txt

@@ -1 +0,0 @@
-Doug Coleman

basis/random/backend/backend.factor

@@ -1,10 +0,0 @@
-! Copyright (C) 2009 Doug Coleman.
-! See http://factorcode.org/license.txt for BSD license.
-USING: cpu.x86.features init kernel namespaces random
-random.mersenne-twister random.sfmt ;
-IN: random.backend
-
-[
-    sse2? [ default-sfmt ] [ default-mersenne-twister ] if
-    random-generator set-global
-] "bootstrap.random" add-init-hook

basis/random/mersenne-twister/mersenne-twister.factor

@@ -76,3 +76,8 @@ M: mersenne-twister random-32* ( mt -- r )
 : default-mersenne-twister ( -- mersenne-twister )
     [ 32 random-bits ] with-system-random
     <mersenne-twister> ;
+
+[
+    default-mersenne-twister random-generator set-global
+] "bootstrap.random" add-init-hook
+

basis/random/random.factor

@@ -112,4 +112,4 @@ PRIVATE>
     { [ os unix? ] [ "random.unix" require ] }
 } cond
 
-"random.backend" require
+"random.mersenne-twister" require