packages: improve license type lists

Make license type lists more uniform:

* put content license applies to in parenthesis; ex: "GPLv2+ (programs)"
* use commas to separate types listed without conjuction; ex: "GPLv2, LGPLv2"

No attempt was made to validate the claimed licenses.  This is just a tweak
to increase uniformity of the _LICENSE variables.

Signed-off-by: Danomi Manchego <danomimanchego123@gmail.com>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
[Thomas: replace semi-colons by commas in LIBURCU_LICENSE.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>