Clarify that the license is GPLv2+

Clarify that the license is GPLv2+

Regarding this license clarification there are 3 commits of interest
(commits A, B, C). Before commit A the COPYING file contained only the
text of the GPLv2 license, while all source files had a license block
at the top saying that they are under the terms of "GPLv2 or later". With
commit A there was a temporary change to GPLv3. The COPYING file contained
only the text of the GPLv3 license, while all source files had a license
block at the top saying that they are under the terms of "GPLv3 or later".
Then with commit B the COPYING file and the license block of the source
files was reverted to their state before commit A. Afterwards, with
commit C a license summary(or clarification) block was put at the top of
the COPYING file. This block indicated that the license was GPLv2 without
having the "or later" clause and it also included the OpenSSL exception.
However, the license block of each source file continued to contain the
"or later" clause which was not removed. The same license block continues
to exist in all current source files. Thus it is concluded that the ommision
of the "or later" clause with commit C in the COPYING file was accidental.
OR ALTERNATIVELY (OR IN ADDITION)
At the time commit C was made Christophe Dumez was not the sole contributor.
There is no record that the other contributors agreed with the supposed
GPLv2 only change or that there was a Contributor License Agreement,
transfering their rights to him. Thus making his license change decision
invalid/void/illegal.

Commit A: 54f9375b325cc03f8d5da9abbf6c4e25e8ee698f
Commit B: 8df61db644a7fcb19170d60da3b7b5297215439c
Commit C: 9835af49627e65d314668387b6ec9d029707c186