Implement new function Client_SearchServer()

This function returns the server structure of a client or a given "mask";
it is useful for implemention handlers for commands like "COMMAND *.net",
which should work on a server matching "*.net".

Please note that the local server is always returned when it matches the
mask, but besides that, the order is completely arbitrary.
irc-info: move static functions at the top of the file
irc-info.c: add/streamline function documentation comments

Add missing comments, streamline wording, and remove references to the
RFCs: this will be added to ./doc/Commands.txt with an other patch and
we want to avoid redundancy ...
Add new irc-macros.h to project

This file prvides some macros for common tasks required by functions
implementing handlers for IRC commands:

 * _IRC_ARGC_LE_OR_RETURN_
 * _IRC_ARGC_GE_OR_RETURN_
 * _IRC_GET_SENDER_OR_RETURN_
 * _IRC_GET_TARGET_SERVER_OR_RETURN_
Update irc-info.c to use irc-macros.h

This includes:

 - move IRC_SetPenalty() at the beginning of the handler functions,
 - use macros provided by irc-macros.h,
 - code cleanup.

The main benefits of this patch are core size reduction, streamlined
structure of the handler functions, and enhanced functionality:
because of the _IRC_GET_TARGET_SERVER_OR_RETURN_() macro using the
Client_SearchServer() function, the target of the specific IRC command
can now be given server names, server mask, or the nickname of a user
connected to the server.

Closes bug #153.
ngIRCd Release 20.2

(cherry picked from commit c45d9dd1f08fddb95fa01d62c69848cd753a3161)
configure: conversation -> conversion
configure: search for iconv_open as well as libiconv_open

On some installations iconv_open() is actually libiconv_open().
iconv_open() is the glibc version while libiconv_open() is the libiconv
version. This patch enables ngIRCd to detect both cases.

Tested on OpenBSD 5.1.

Closes bug #151.
Merge branch 'bug153-ServerMask' into master

* bug153-ServerMask:
  Update irc-info.c to use irc-macros.h
  Add new irc-macros.h to project
  irc-info.c: add/streamline function documentation comments
  irc-info: move static functions at the top of the file
  Implement new function Client_SearchServer()

Conflicts:
	src/ngircd/irc-info.c
Merge branch 'bug151-iconv' into master

* bug151-iconv:
  configure: search for iconv_open as well as libiconv_open
irc-login.c: conenction -> connection

Introduced by commit d3ef2239 as of Sun Jan 16 2011 ...
Thanks to Patrik Schindler <poc@pocnet.net> for reporting this!
src/testsuite/README: add whois-test.e
Clean up Xcode project file, remove outdated files, add missing
Update Doxygen configuration
irc-cap.c: move static functions to the top of the file

And remove now unnecessary (local) prototypes.
Add new _IRC_ARGC_BETWEEN_OR_RETURN_ macro to irc-macros.h
Add new _IRC_ARGC_EQ_OR_RETURN_ macro to irc-macros.h
irc-cap.c: Update source code documentation
irc-op.c: Update source code documentation
irc-cap.c: use irc-macros.h