Experimental feature of saving buffers within savegame files (in extended section...

Experimental feature of saving buffers within savegame files (in extended section). Code needs cleaning (since i'm not really understand concept of expandable arrays). Upgraded buf_create() to optional buf_create(string,float) string being a buffer format (yet another experimental feature that will be tested in future), should be "string" if presented. Second float is buffer flags, currently only flag 1 (save in savegames) are used. There is idea for another buffer flag which will allow buffer to pass across levels, saving handle number and contents (bufhandle could be passed as one of parm*).

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@9949 d7cf8633-e32d-0410-b094-e92efae38249