Avoid doc-comment in header as they are interpreted by g-ir-scanner, fix a typo,
remove empty lines, add to change log.

- remove any notion of deprecation of legacy symbol names
- make sure typelib search path is set for test program
- add separate test target to test/gi/makefile
- improve g-ir-scanner call command line
- fixed gtk2 support of test test/gi/gi-test.py

The test suite acts also as an example for downstream projects to generate
gobject-introspection data. A known-good .gir file is checked in for checking
results in the future. Lastly, a small python uses the gobject-introspection
data to create a small editor window.

The change to gtk/makefile is because scintilla needs to be in a shared library
for the python program. Therefore scintilla.a has to be compiled with -fPIC.