Companies like Google now respond to HTTP requests with HTTP 2. 
For example:

  curl --silent --head https://www.google.com

returns the first line

  HTTP/2 200

The Guile HTTP client code expects a “HTTP/x.y” structure, and 
treats this as an error.  This patch recognizes and handles 
“HTTP/2” on input and output.  HTTP version numbers don’t 
proliferate quickly, so the code uses a brute force approach for 
now.