The goal is to change the version number for a new release only in
CMakeLists.txt. This is the second step.
This commit also adds a chapter "Migrating Code from FLTK 1.4 to 1.5".
Details:
- documentation/CMakeLists.txt: configure 'version.dox'
- fluid/documentation/CMakeLists.txt: same as above
- documentation/Doxyfile.in: add "Migrating Code from FLTK 1.4 to 1.5"
- documentation/src/index.dox: include 'version.dox' and 'migrating...'
- fluid/documentation/src/index.dox: same as above
- documentation/src/preface.dox: include 'version.dox'
- documentation/version.dox.in: input to CMake configure 'version.dox'
- fluid/documentation/version.dox.in: same as above
- documentation/src/migration_1_4.dox: update links
- documentation/src/migration_1_5.dox: new documentation chapter
