qmake: No more exporting symbols out of the executable

Adjusted the build settings in the qmake project files so that no more
symbols are exported out of the executables. This has been a long-time
annoyance and a kludge that is now finally being removed. In the future,
exports will be handled manually in a way that allows plugins to work
with any executable (client or server).
Server: Omit Updater in server build

The server does not need to have the automatic updater.
Merge branch 'master' into separate-server
Relocated dd_snprintf to libdeng1
Defined new API exchange mechanism

The plugins must export an entry point called deng_API() that the
engine will use to pass API structs to.

Todo: Engine must call deng_API to supply all available public APIs
when loading a library.
Publish the Uri module and W APIs

The Library loader now calls deng_API() to publish all the public
APIs.

Added api/de_api.h for the generic/base API struct and macro
declarations.
Document the engine version where each public API is first available
Added public APIs for Plug and Def modules

Also cleaned up the API macros a little and added a separate header
for the public Def API.
Added the F module public API (file system)

The public headers that define module APIs now use an "api_" prefix.
Added a public API for Base domain

Also fixed build regarding internal use of the public F API.
Added a public API for the Con module

Only includes Con_Message at this stage.
Added a public API for the map editor (MPE)
Added public API for Material module

Now the wadmapconverter and dehread plugins compile and link
successfully.
Cleanup
libdoom: Import available public APIs
Added public API for the busy mode
Added public API for FR (Font Render) module

In the server build, the FR API is not available at all.
Added public API for Thinker; renamed header and functions
API identifiers should default to the latest version when compiling

Each identifier both version specific (e.g., "v1") and a "latest"
variant.
Added public API for B (Bindings) and more Con API functions