zdev: Implement internal device attributes

This change adds base infrastructure for implementing internal device
attributes. In the context of the zdev tools, an internal device
attribute is a new type of device attribute with the following
characteristics:

  - Can be set and removed like normal device attributes
  - Affects zdev-internal handling only
  - Does not correspond to an actual device attribute, that is
    it has no representation in SysFS
  - Can not be set in the active configuration
  - Name starts with "zdev:" to prevent conflicts with actual
    device attributes

Values for internal device attributes are stored in udev rules alongside
the normal persistent configuration of a device. They are encoded as
udev environment variables. Note that they have no further effect on
udev processing.

Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zdev/src/misc.c

@@ -1717,3 +1717,18 @@ void debug_init(int argc, char *argv[])
 		fprintf(stderr, "%s\"%s\"", i > 0 ? ", " : "", argv[i]);
 	fprintf(stderr, "\n");
 }
+
+/* Return the last occurrence of @needle in @haystack, or %NULL if @needle
+ * was not found. */
+char *misc_strrstr(const char *haystack, const char *needle)
+{
+	char *result, *next;
+
+	result = strstr(haystack, needle);
+	if (result) {
+		while ((next = strstr(result + 1, needle)))
+			result = next;
+	}
+
+	return result;
+}