Reworked gtk3-client Freeciv theme to work around theme engine bug making it extremely slow.

See bug #21726


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25128 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Added missing function headers to helpdlg.c in gui-sdl and gui-sdl2.
Also touched coding style a lot.

See patch #2937


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25130 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Added support for special value "test" for --enable-ruledit.

See patch #4790


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25131 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Avoid short burst of menu music when switching player

Reported by Jacob Nevins <jtn>

See bug #22077


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25132 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Documented gtk3-client as new default client since 2.5.

See patch #4772


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25137 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Removed unused alphablit.c from gui-sdl2 from under version control.

See patch #4793


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25138 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Fixed SECFILE_RETURN_VAL_IF_FAIL macro uses to return value of correct type
for the functions they are used in.

Reported by David Lowe <doctorjlowe>

See bug #19307


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25139 a0f10bec-cc02-0410-94fc-a9cfff90b4cd