add --disable-asm flag for disabling inline asm

Surprisingly (or not), a lot of OpenSSL's inline assembly actually makes
things slower with a relatively modern compiler (read, gcc >= 4.x).

configure.ac

@@ -165,6 +165,10 @@ AC_ARG_WITH([enginesdir],
 	AC_DEFINE_UNQUOTED(ENGINESDIR, "$withval")
 )
 
+AC_ARG_ENABLE([asm],
+	AS_HELP_STRING([--disable-asm], [Disable assembly]))
+AS_IF([test "x$enable_asm" == "xno"], [CFLAGS="$CFLAGS -DOPENSSL_NO_ASM"])
+
 LT_INIT
 
 AC_CONFIG_FILES([