doxygen: automate versioning and names

Removes the need to maintain the project name, version and source
directory in the doxygen files.

API and ABI versions should be in one place only.

Change-Id: If26c7ac1166b519d0ceae91b3656b55c4601b52d
Reviewed-by: Sebastien Blin <sebastien.blin@savoirfairelinux.com>

doc/doxygen/core-doc.cfg.in

@@ -25,13 +25,13 @@ DOXYFILE_ENCODING      = UTF-8
 # The PROJECT_NAME tag is a single word (or a sequence of words surrounded
 # by quotes) that should identify the project.
 
-PROJECT_NAME           = "Ring Daemon"
+PROJECT_NAME           = @PROJECT_NAME@
 
 # The PROJECT_NUMBER tag can be used to enter a project or revision number.
 # This could be handy for archiving the generated documentation or
 # if some version control system is used.
 
-PROJECT_NUMBER         = 7.1.0
+PROJECT_NUMBER         = @PACKAGE_VERSION@
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer
@@ -610,7 +610,7 @@ WARN_LOGFILE           =
 # directories like "/usr/src/myproject". Separate the files or directories
 # with spaces.
 
-INPUT                  = ../../src
+INPUT                  = @top_srcdir@
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding, which is