Remove Fl::*sleep() method family, as discussed in fltk.coredev.

Hopefully this doesn't break Windows or Mac OX IDE builds, please help
testing.

Short story: these functions showed compatibility problems, lacked some
quality (regarding interruption by signals), and maybe more.

This is a combined commit that reverts three (3) svn commits. The following
lists are extracted from git, but show the svn revisions and files:

    Remove Fl::*sleep() family, part 1: revert svn r 10287.

:100644 100644 a988702... 794920f... M	ide/Xcode4/FLTK.xcodeproj/project.pbxproj

    Remove Fl::*sleep() family, part 2: revert svn r 10151.

:100644 100644 cf839e6... bfde9c4... M	ide/Xcode3/FLTK.xcodeproj/project.pbxproj
:100644 100644 794920f... c0c772a... M	ide/Xcode4/FLTK.xcodeproj/project.pbxproj

    Remove Fl::*sleep() family, part 2b: revert svn r 10151 (continued).

:100644 100644 bfde9c4... abf2922... M	ide/Xcode3/FLTK.xcodeproj/project.pbxproj

    Remove Fl::*sleep() family, part 3: revert svn r 10150.

:100644 100644 b469018... e76a3e5... M	FL/Fl.H
:100644 100644 7bb7899... 4d4755d... M	ide/VisualC2008/fltk.lib.vcproj
:100644 100644 9d9a2cf... 334aef8... M	ide/VisualC2008/fltkdll.vcproj
:100644 100644 5533a54... e30058b... M	ide/VisualC2010/fltk.lib.vcxproj
:100644 100644 e49f691... 1259c87... M	ide/VisualC2010/fltk.lib.vcxproj.filters
:100644 100644 946f31a... d53ab80... M	src/CMakeLists.txt
:100644 000000 fed36fd... 0000000... D	src/Fl_sleep.cxx
:100644 100644 3d9656c... 3b265f9... M	src/Makefile
:100644 100644 6eadbcb... 5dd5872... M	test/sudoku.cxx


git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10419 ea41ed52-d2ee-0310-a9c1-e6b18d33e121