udev: convert to virtual package

This patch converts udev to a virtual package. For the moment, there is only
one provider for the udev features: eudev.

Packages meant to provide udev-like features must select the symbol
BR2_PACKAGE_HAS_UDEV.

Packages depending on BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_UDEV or
BR2_PACKAGE_UDEV have been converted to use the new symbol.

[Peter: move legacy symbols under 2014.05]
Signed-off-by: Eric Le Bihan <eric.le.bihan.dev@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
diff --git a/package/usbmount/Config.in b/package/usbmount/Config.in
index 2583e7c..0bb8883 100644
--- a/package/usbmount/Config.in
+++ b/package/usbmount/Config.in
@@ -1,6 +1,6 @@
 config BR2_PACKAGE_USBMOUNT
 	bool "usbmount"
-	depends on BR2_PACKAGE_UDEV
+	depends on BR2_PACKAGE_HAS_UDEV
 	select BR2_PACKAGE_LOCKFILE_PROGS
 	help
 	  The usbmount package automatically mounts USB mass storage devices
@@ -9,4 +9,4 @@
 	  http://usbmount.alioth.debian.org/
 
 comment "usbmount requires udev to be enabled"
-	depends on !BR2_PACKAGE_UDEV
+	depends on !BR2_PACKAGE_HAS_UDEV