The _FVH header is the actual fixed header, the GUID identifies the type of
filesystem instead. Since this seems to be the only known GUID valid for
this structure, accept it by itself, and report the size of the volume and
header.

Identify the GUIDs for EFI Capsule formats, both v0.9, v2 and UEFI
versions, which are essentially the same for what gets reported.

In Python 3.4, if the interpreter is launched with e.g. LANG=C environment,
binwalk fails with UnicodeDecodeError, since it tries to decode included
magic files (such as src/binwalk/magic/linux) with ascii codec. This patch
makes sure that utf-8 codec is always used.