Add support for konsole 24-bit color mode

Konsole provides the \e[38;2;R;G;Bm and \e[48;2;R;G;Bm terminal
sequences to set the foreground and background, respectively, to the
24-bit (R,G,B) tuple.  This allows Vim to use that sequence to allow
terminal vim to use the same colors as gvim.

The check to enable 24-bit color is that the terminal color setting is
greater than 256.

Also overrides has('gui_running') to return 1, since many colorschemes
rely on that being true to set the guifg= and guibg= attributes.

Hard-coded version of X11's rgb.txt is hackish at best, but prevents
having to use any X11 functionality to resolve color names.

patch 7.4.1022

Problem:    The README file contains some outdated information.
Solution:   Update the information about supported systems.

patch 7.4.1021

Problem:    Some makefiles are outdated.
Solution:   Add a note to warn developers.

patch 7.4.1020

Problem:    On MS-Windows there is no target to run tests with gvim.
Solution:   Add the testgvim target.

patch 7.4.1019

Problem:    Directory listing of "src" is too long.
Solution:   Rename the resources file to make it shorter.

patch 7.4.1018

Problem:    Failure running tests.
Solution:   Add missing change to list of old style tests.

patch 7.4.1017

Problem:    When there is a backslash in an option ":set -=" doesn't work.
Solution:   Handle a backslash better. (Jacob Niehus)  Add a new test, merge
            in old test.

patch 7.4.1016

Problem:    Still a few OS/2 pieces remain.
Solution:   Delete more.

patch 7.4.1015

Problem:    The column is not restored properly when the matchparen plugin is
            used in Insert mode and the cursor is after the end of the line.
Solution:   Set the curswant flag. (Christian Brabandt).  Also fix
            highlighting the match of the character before the cursor.

patch 7.4.1014

Problem:    fnamemodify('.', ':.') returns an empty string in Cygwin.
Solution:   Use CCP_RELATIVE in the call to cygwin_conv_path. (Jacob Niehus,
            closes vim#505)