godoc/util: serve SVG files raw
godoc/util: serve SVG files raw

When a godoc Presentation is serving a file, it will sniff its
contents to determine if it contains "human-readable" text. If
it does, then it serves the contents of the file with surrounding
HTML. SVG files should not be served with any additional HTML even
though their contents are not a binary format (just like CSS or JS
files).

Updates golang/go#9936

Change-Id: Id3dd3b6cda4f103b08f6e924923426a86bd46ec8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/177498
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools