x86, um: switch to generic fork/vfork/clone

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 46c3bff..0df6e7d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -112,6 +112,7 @@
 	select GENERIC_KERNEL_EXECVE
 	select MODULES_USE_ELF_REL if X86_32
 	select MODULES_USE_ELF_RELA if X86_64
+	select CLONE_BACKWARDS if X86_32
 
 config INSTRUCTION_DECODER
 	def_bool y