Merge #16347: doc: Include static members in Doxygen

84ad4d2 doc: Include static members in Doxygen (Carl Dong)

Pull request description:

  This makes our Doxygen output more useful by generating them for static members.

ACKs for top commit:
  practicalswift:
    ACK 84ad4d2
  laanwj:
    ACK bitcoin/bitcoin@84ad4d2
  fanquake:
    ACK 84ad4d2

Tree-SHA512: f47fe6f36739ba8d7978169b28a29ad3d0796d7535052e447740077f4827c9bf5082d14c9cac2fbaf91f01bb2bffc25d9d7c3f702c0848c79a48a311ebd3344f

Author: laanwj

doc/Doxyfile.in

@@ -453,7 +453,7 @@ EXTRACT_PACKAGE        = NO
 # included in the documentation.
 # The default value is: NO.
 
-EXTRACT_STATIC         = NO
+EXTRACT_STATIC         = YES
 
 # If the EXTRACT_LOCAL_CLASSES tag is set to YES, classes (and structs) defined
 # locally in source files will be included in the documentation. If set to NO,