Add Fl_Flex widget from Karsten Pedersen (issue #255)

This work is based on the repository and latest commit:
  https://github.com/osen/FL_Flex.git

  commit 36e4ed75a00daac825b87e81295818b4650991f5
  Author: Karsten Pedersen <...>
  Date:   Fri Apr 23 12:06:16 2021 +0000

    Added Fltk (LGPL) license.

This widget is similar to Fl_Pack and supports either one row or one
column of widgets but has some more features. Test and demo programs
are included:

  test/flex_login.cxx: simple "login window" demo program
  test/flex_demo.cxx:  slightly more complex demo program

The original demo programs can still be compiled and built with
the new widget provided you '#include <FL/Fl_Flex.H>'.
Backwards compatible methods are included (except debug()).

The original widget has been modified to match FLTK standards and
enhanced in several ways, including:

- support box frames
- add HORIZONTAL and VERTICAL enum values (as in Fl_Pack)
- add horizontal() method (as in Fl_Pack)
- use type() rather than internal 'direction' variable
- add standard widget constructor (x, y, w, h, label)
- add margin and gap accessors rather than hard coding constants
- improve test and demo programs
- add documentation
- replace <vector> with array as required by FLTK CMP
- rename camelCase method names, keeping old names for compatibility:
  - change 'setSize(Fl_Widget*, int)'   to 'set_size(Fl_Widget*, int)'
  - change 'bool isSetSize(Fl_Widget*)' to 'int set_size(Fl_Widget*)'
- remove debug() method
- add a way to "unset" fixed size: set_size(Fl_Widget *, 0)
- add layout() method to force recalculation of children
- unify resizeRow() and resizeCol() methods to avoid code duplication
- improve widget size calculation.

1 files changed, 40 insertions, 0 deletions

diff --git a/test/makedepend b/test/makedepend
index 3fbcd2262..a3e88fdd3 100644
--- a/test/makedepend
+++ b/test/makedepend
@@ -857,6 +857,46 @@ file_chooser.o: ../FL/Fl_Valuator.H
 file_chooser.o: ../FL/Fl_Widget.H
 file_chooser.o: ../FL/Fl_Window.H
 file_chooser.o: ../FL/platform_types.h
+flex_demo.o: ../FL/Enumerations.H
+flex_demo.o: ../FL/Fl.H
+flex_demo.o: ../FL/Fl_Bitmap.H
+flex_demo.o: ../FL/Fl_Box.H
+flex_demo.o: ../FL/Fl_Button.H
+flex_demo.o: ../FL/Fl_Cairo.H
+flex_demo.o: ../FL/fl_casts.H
+flex_demo.o: ../FL/fl_config.h
+flex_demo.o: ../FL/Fl_Double_Window.H
+flex_demo.o: ../FL/Fl_Export.H
+flex_demo.o: ../FL/Fl_Flex.H
+flex_demo.o: ../FL/Fl_Group.H
+flex_demo.o: ../FL/Fl_Image.H
+flex_demo.o: ../FL/Fl_Input.H
+flex_demo.o: ../FL/Fl_Input_.H
+flex_demo.o: ../FL/fl_types.h
+flex_demo.o: ../FL/fl_utf8.h
+flex_demo.o: ../FL/Fl_Widget.H
+flex_demo.o: ../FL/Fl_Window.H
+flex_demo.o: ../FL/platform_types.h
+flex_login.o: ../FL/Enumerations.H
+flex_login.o: ../FL/Fl.H
+flex_login.o: ../FL/Fl_Bitmap.H
+flex_login.o: ../FL/Fl_Box.H
+flex_login.o: ../FL/Fl_Button.H
+flex_login.o: ../FL/Fl_Cairo.H
+flex_login.o: ../FL/fl_casts.H
+flex_login.o: ../FL/fl_config.h
+flex_login.o: ../FL/Fl_Double_Window.H
+flex_login.o: ../FL/Fl_Export.H
+flex_login.o: ../FL/Fl_Flex.H
+flex_login.o: ../FL/Fl_Group.H
+flex_login.o: ../FL/Fl_Image.H
+flex_login.o: ../FL/Fl_Input.H
+flex_login.o: ../FL/Fl_Input_.H
+flex_login.o: ../FL/fl_types.h
+flex_login.o: ../FL/fl_utf8.h
+flex_login.o: ../FL/Fl_Widget.H
+flex_login.o: ../FL/Fl_Window.H
+flex_login.o: ../FL/platform_types.h
 fltk-versions.o: ../FL/Enumerations.H
 fltk-versions.o: ../FL/Fl.H
 fltk-versions.o: ../FL/fl_ask.H