Add syntax highlighting for SELinux kernel policy language
This corresponds to the standard policy language of SELinux , used for example, by the SELinux Reference Policy  or the Android policies .
Extensions and files to highlight:
- SELinux Type Enforcement (*.te)
- SELinux Interface File (*.if)
- M 4 Macros of Reference Policy (*.spt)
- Some policy build files and policy config. files (access_vectors, mls, mcs, mls_macros, te_macros, policy_capabilities, seapp_contexts, port_contexts), and monolithic policy (policy.conf). NOTE: I added only relevant configuration files and policy building, since many have very generic names.
Also, this file contains common rules and keywords between selinux-fc.xml and selinux-cil.xml. For example, it contains the RegExp highlighting and the Permissions keywords. The idea is to avoid having repeated keywords and rules between the SELinux highlighting files.
 SELinux Wiki. PolicyLanguage: https://selinuxproject.org/page/PolicyLanguage#Kernel_Policy_Language
 SELinux Reference Policy: https://github.com/SELinuxProject/refpolicy/wiki
 Security-Enhanced Linux in Android: https://source.android.com/security/selinux/
 SELinux policy configuration for AOSP: https://android.googlesource.com/platform/system/sepolicy/
Reviewers: Framework: Syntax Highlighting, dhaumann, cullmann
Reviewed By: Framework: Syntax Highlighting, cullmann
Subscribers: kwrite-devel, kde-frameworks-devel
Differential Revision: https://phabricator.kde.org/D15089