Merge branch 'master' into core-updates

Note: this merge actually changes the 'curl' and 'python-attrs' derivations,
as part of solving caf4a7a277 and
12964df69a respectively.

4604d43c0e (gnu: gnutls@3.6.16: Fix cross-compilation.) was ignored because it
cannot currently be tested.

 Conflicts:
	gnu/local.mk
	gnu/packages/aidc.scm
	gnu/packages/boost.scm
	gnu/packages/curl.scm
	gnu/packages/nettle.scm
	gnu/packages/networking.scm
	gnu/packages/python-xyz.scm
	gnu/packages/tls.scm

gnu/packages/documentation.scm

@@ -334,7 +334,7 @@ local system.")
       (inputs
        `(("libarchive" ,libarchive)
          ("sqlite" ,sqlite)
-         ("qtbase" ,qtbase)
+         ("qtbase" ,qtbase-5)
          ("qtdeclarative" ,qtdeclarative)
          ("qtwebchannel" ,qtwebchannel)
          ("qtwebengine" ,qtwebengine)