Fix error in approximation to (line-number-at-pos (point-max))

ggtags-global-output-lines >= (line-number-at-pos (point-max)) is not
always true.
Refactor out ggtags-include-file from ggtags-find-tag-dwim

Do not move point to the beginning of line if ggtags-include-pattern
is a function otherwise it cannot access the value of point.