Make each convenience library depend on the ones it requires, which is
pretty straightforward for us as they each only depend on a single
other one, avoiding any worry about double linking of static objects.
The flags in this variables are used to tune the linker behavior on the
final libgeany (currently set the version information), so should only
used on really linked libraries, not Libtool helper libraries.
Checks if the compiler supports -fvisibility and the linker supports
-dynamic-list arguments and use them instead of hardcoding. The new
geany-lib.m4 also accomodates future use of Libtool versioning.
This will allow plugins to link against the core when accessing API
functions, now that the macro/struct/funcptr stuff is gone.
Also convert the helper libraries into Libtool helper libraries as
linking a shared library against static libraries is (apparently) not
portable.
Split ctags and tagmanager sources, as follows:
tagmanager/ctags: the parsers, more or less upstream CTags;
tagmanager/mio: local MIO library copy;
tagmanager/src: actual tagmanager sources.
