[CMake] Fix CMake 3.1 warning about new policy CMP0053.

CMake Warning (dev) at CMake/export.cmake:48 (set):
  Policy CMP0053 is not set: Simplify variable reference and escape sequence
  evaluation.  Run "cmake --help-policy CMP0053" for policy details.  Use the
  cmake_policy command to set the policy and suppress this warning.

Changed old-style @variable@ replacement to ${variable}. 


git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10467 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Change necessary now that there are true FLTK sub-windows on the Mac OS X platform.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10468 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Fix a doxygen warning.


git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10469 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Separate and improve documentation of overloaded Fl::event_state() methods.


git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10470 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Update CREDITS file.


git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10471 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Corrected case when using retina display.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10472 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Improve tooltip behavior for huge tooltips: remove flicker, support key/mouse dismiss

Fixes STR 2650.


git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10473 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Improve code formatting according to CMP.

Add one pair of braces for clarity, move some other braces and
else statements around. There's more to that, but these were
minimal changes to improve readability for solving STR #3043.
There are no real code changes involved though.


git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10474 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Make sure that subwindows won’t leak out of their parent window 
even if they have coordinates that would provoke it.  

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10475 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Extend advanced.dox multithreading to add additional caveats
about the use of show() and hide() from child threads, based
on issues reported in fltk.general with tooltip windows
causing issues.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10476 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Improved processing of retina displays: replace [NSWindow backingScaleFactor] that is not recommended.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10477 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Removed subwindow-specific code that is no longer needed with true subwindows.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10478 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Removed statement that became incorrect with true Mac OS X subwindows.


git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10479 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Removed one use of dynamic_cast.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10480 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Improved handling of high resolution ("retina") displays.
The new field bool Fl_X::mapped_to_retina is updated when needed, that is, when the window is moved.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10481 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Propagate Fl_X::mapped_to_retina value from parent to subwindows.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10482 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Fix case when show() of a subwindow whose parent is not shown yet.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10483 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
It is necessary to compute Fl_X::mapped_to_retina after the window is mapped
because the windowDidMove notification is not always sent.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10484 ea41ed52-d2ee-0310-a9c1-e6b18d33e121