break up event-log-tags; generate java source files with constants

break up event-log-tags; generate java source files with constants

Construct the /system/etc/event-log-tags file by unioning together any
*.logtags files included in LOCAL_SRC_FILES throughout the system (with
appropriate error checking for dup tag numbers, etc.)

For java packages, generate a java source file from the logtags file for
that package that contains static integer constants for each tag name.