FOR_ALL_TABS helper
FOR_ALL_WINDOWS_IN_TAB and local variables in FOR_ALL_TAB_WINDOWS
Expand FOR_ALL_WINDOWS to FOR_ALL_WINDOWS_IN_TAB(curtab)
Merge pull request #1108 from war1025/dev/for_all_tabs

FOR_ALL_TAB_WINDOWS cleanup. Add FOR_ALL_TABS and FOR_ALL_WINDOWS_IN_TAB.
Add EndOfBuffer highlight group