core: move NFD_VERSION{,_BUILD}_STRING to version.cpp

Change-Id: I97c23de24d8a176bb83a8f481f4880ff49ea710d
diff --git a/docs/doxygen.conf.in b/docs/doxygen.conf.in
index 5ca87f3..4efad0a 100644
--- a/docs/doxygen.conf.in
+++ b/docs/doxygen.conf.in
@@ -780,7 +780,7 @@
 # spaces. See also FILE_PATTERNS and EXTENSION_MAPPING
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = core daemon tools
+INPUT                  = core daemon tools build/core/version.hpp
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses