Add permission expression parser

Introduces a new parser for permission expressions intended to be used
for the AIDL annotation @Enforce. An example of expression it can parse
is:

  "permission = READ_PHONE_STATE || uid = SYSTEM_UID"

The parser is generated using Bison and Flex. It declares it own prefix
and namespace to avoid name conflict when used within libaidl-common.

Test: aidl-perm_unittests
Bug: 197828948
Change-Id: Iac10fdcf92a1437ec6d4e6b9b90c063cc5415e8b
6 files changed