Doxyfile: set "EXTRACT_ALL" to "YES"

This avoids the need to add "@file" to every file we want to generate documentation for.

Doxyfile

@@ -321,7 +321,7 @@ SYMBOL_CACHE_SIZE      = 0
 # Private class members and static file members will be hidden unless 
 # the EXTRACT_PRIVATE and EXTRACT_STATIC tags are set to YES
 
-EXTRACT_ALL            = NO
+EXTRACT_ALL            = YES
 
 # If the EXTRACT_PRIVATE tag is set to YES all private members of a class 
 # will be included in the documentation.