From didier gautheron: remove redundant or use faster col_xxx functions

From didier gautheron: remove redundant or use faster col_xxx functions

- when the text parameter is constant col_add_str() and col_set_str() are equivalent but col_set_str() is faster.
- same for  replace col_append_fstr and col_append_str
- remove col_clear() when it's redundant:
    + before a col_set/col_add if the dissector can't throw an exception.
- replace col_append() after a col_clear() with faster col_add... or col_set

   https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=9344

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@52948 f5534014-38df-0310-8fa8-9805f1628bb7