selinux: declare data arrays const

The arrays for the policy capability names, the initial sid identifiers
and the class and permission names are not changed at runtime.  Declare
them const to avoid accidental modification.

Do not override the classmap and the initial sid list in the build time
script genheaders.

Check flose(3) is successful in genheaders.c, otherwise the written data
might be corrupted or incomplete.

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
[PM: manual merge due to fuzz, minor style tweaks]
Signed-off-by: Paul Moore <paul@paul-moore.com>