[phobos] New Linux phobos shared library

[Jordi Sayol]

 From dmd v2.063, release zip file includes Linux phobos shared libraries. As shared libraries are needed at runtime too, we should allow to install multiple versions of phobos shared libs. at same time. If not, every program compiled against it will be forced to be recompiled every new dmd/phobos release. To avoid this, phobos shared libs. should include some version number on its name.

I propose to name the shared phobos library as "libphobos2.so.0.nn.0", where "nn" is the current dmd version. The last zero is just for bug/regression fixes.

As phobos changes its interface (almost) every new release, I propose to set its SONAME to "libphobos2.so.0.nn", so when phobos become stable we can change the library name to "libphobos2.so.1.0.0" and its SONAME to "libphobos2.so.1".

Some info about Linux shared libraries:
http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html

-- 
Jordi Sayol