docs: Update to secure URL versions

docs/CODE_OF_CONDUCT.md

@@ -28,5 +28,5 @@ reported by opening an issue or contacting one or more of the project
 maintainers.
 
 This Code of Conduct is adapted from the [Contributor
-Covenant](http://contributor-covenant.org), version 1.1.0, available at
-[http://contributor-covenant.org/version/1/1/0/](http://contributor-covenant.org/version/1/1/0/)
+Covenant](https://contributor-covenant.org/), version 1.1.0, available at
+[https://contributor-covenant.org/version/1/1/0/](https://contributor-covenant.org/version/1/1/0/)

docs/TODO

@@ -210,7 +210,7 @@
 1.5 get rid of PATH_MAX
 
  Having code use and rely on PATH_MAX is not nice:
- http://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html
+ https://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html
 
  Currently the SSH based code uses it a bit, but to remove PATH_MAX from there
  we need libssh2 to properly tell us when we pass in a too small buffer and

include/README

@@ -30,4 +30,4 @@ NOTE FOR LIBCURL HACKERS
 
 To figure out how to do good and portable checks for features, operating
 systems or specific hardwarare, a very good resource is Bjorn Reese's
-collection at http://predef.sf.net/
+collection at https://sourceforge.net/p/predef/wiki/