Fix tagging of class members in C-like OO languages

Fix tagging of class members in C-like OO languages

* lib-src/etags.c (longopts): Add new option --class-qualify and
its shorthand -Q.
(print_help): Add help text for --class-qualify.
(main): Add handling of -Q.
(consider_token, C_entries) <omethodparm>: Append argument types
to Objective C methods only if --class-qualify was specified.
Qualify C++, Objective C, and Java class members with their class
names only if --class-qualify was specified.
(C_entries): If --class-qualify was not specified, remove the
namespace and class qualifiers from tag names of C++ methods.
This allows to use etags.el as xref back-end without the
tag-symbol-match-p method, which greatly increases the number of
potentially false positives.  (Bug#20629)

* doc/man/etags.1: Update to document the new --class-qualify
option.

* test/etags/ETAGS.good_1:
* test/etags/ETAGS.good_2:
* test/etags/ETAGS.good_3:
* test/etags/ETAGS.good_4:
* test/etags/ETAGS.good_5:
* test/etags/CTAGS.good: Update due to changes in etags.c.