package/bitcoin: add CPE variables
cpe:2.3:a:bitcoin:bitcoin_core is a valid CPE identifier for this
package:
https://nvd.nist.gov/products/cpe/search/results?namingFormat=2.3&keyword=cpe%3A2.3%3Aa%3Abitcoin%3Abitcoin_core
Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>