gtags segment fault when read from file.

[Jianbin Kang]

Hello, bug-global
     If gtags read its input files from a file list (use -f option),
and the input files aren't in
     the working directory or its sub-directory of gtags, it will segment fault.
    It seems that the function 'normalize' in libutil/file.c, line 623
will return NULL,
    which causes the problem.



                       yours

    Jianbin Kang