Remove $Id$ tags, update URL's, and more

- remove obsolete svn '$Id$' tags from all source files
- update .fl files and generated files accordingly
- replace 'http://www.fltk.org' URL's with 'https://...'
- replace bug report URL 'str.php' with 'bugs.php'
- remove trailing whitespace
- fix other whitespace errors flagged by Git
- add and/or fix missing or wrong standard headers
- convert tabs to spaces in all source files

The only relevant code changes are in the fluid/ folder where
some .fl files and other source files were used to generate
the '$Id' headers and footers.

Makefile

@@ -1,6 +1,4 @@
 #
-# "$Id$"
-#
 # Top-level makefile for the Fast Light Tool Kit (FLTK).
 #
 # Copyright 1998-2010 by Bill Spitzak and others.
@@ -9,11 +7,11 @@
 # the file "COPYING" which should have been included with this file.  If this
 # file is missing or damaged, see the license at:
 #
-#      http://www.fltk.org/COPYING.php
+#      https://www.fltk.org/COPYING.php
 #
-# Please report all bugs and problems on the following page:
+# Please see the following page on how to report bugs and issues:
 #
-#      http://www.fltk.org/str.php
+#      https://www.fltk.org/bugs.php
 #
 
 include makeinclude
@@ -133,8 +131,3 @@ clang:
 	scan-build -V -k -o `pwd`/clang $(MAKE) $(MFLAGS) clean all
 clang-changes:
 	scan-build -V -k -o `pwd`/clang $(MAKE) $(MFLAGS) all
-
-
-#
-# End of "$Id$".
-#