Move most Drizzle symbols into a shared lib

Change the build setup to build almost all of the symbols in the server as a libdrizzled .so file, and then have a very small main.cc which builds and links in libdrizzled to make a drizzled executable.

Upshots are:
- linktime-binding of plugin symbols
- library link versioning with symbols
- can start to use symbol visibility on the server to explicitly make various symbols either part of the API or not
- track API breakages via objdump