Patch 7.2.055

Patch 7.2.055
Problem:    Various compiler warnings with strict checking.
Solution:   Avoid the warnings by using return values and renaming.
Files:      src/diff.c, src/eval.c, src/ex_cmds.c, src/ex_docmd.c,
            src/fileio.c, src/fold.c, src/globals.h, src/gui.c,
            src/gui_at_sb.c, src/gui_gtk_x11.c, src/gui_xmdlg.c,
            src/gui_xmebw.c, src/main.c, src/mbyte.c, src/message.c,
            src/netbeans.c, src/option.c, src/os_unix.c, src/spell.c,
            src/ui.c, src/window.c

git-svn-id: https://vim.svn.sourceforge.net/svnroot/vim/branches/vim7.2@1270 2a77ed30-b011-0410-a7ad-c7884a0aa172