Update year in copyright headers.

Done with

	files=$(git grep -l 'Copyright (C) [0-9]\{4\}\(-2014\)* Andre Noll')
	sed --in-place= -e 's/Copyright (C) \([0-9]\{4\}\)-2014 Andre Noll/Copyright (C) \1 Andre Noll/1' $files

In previous years we ran a similar script to set the second year in
the range to the current year. This is kind of silly, so let's get
rid of this useless information.

This commit replaces "Copyright (C) A-B" by "Copyright (C) A" in
all file headers, i.e. only the first year (A) is left in. Accurate
information including time stamps for each change can be obtained
from the git history.