Updated global to 6.5.5.

Version 6.5.5 - Sep 21 2016

This is a bug fix release.

[FIXED BUGS]
o exuberant-ctags.la: The path name of ctags command couldn't changed.
  Now, it can be changed by configuration variable 'ctagscom'.
o Tag files got corrupted when the built-in C++ parser gave up parsing and aborted.
  Now, it is avoided.

o Some inappropriate error messages was changed.

  Error1: NULL file (file size == 0)

$ cp /dev/null GTAGS
$ global -x main

(GLOBAL-6.5.4) global: /tmp/test/GTAGS seems older format. Please remake tag files.
(GLOBAL-6.5.5) global: /tmp/test/GTAGS seems to be corrupted.

  Error2: Corrupted file

$ echo aaa >GTAGS
$ global -x main

(GLOBAL-6.5.4) global: GTAGS not found.
(GLOBAL-6.5.5) global: /tmp/test/GTAGS seems to be corrupted.

(wiz)