'[[:alpha:]][[:alnum:]_]*' (i.e. a single alpha followed by any number
of alphanumerics or underscores). Unfortunately, the code that expends
variables inside a profile does not match this, it incorrectly matched
'([[:alpha:]]|_)+' (one or more alphas or underscores). This patch
corrects the behavior there as well as synchronizing the expected
variable names in the apparmor.d manpage and apparmor.vim syntax file.

It also adds unit tests and testcases to verify the behavior.

Signed-off-by: Steve Beattie <sbeattie@ubuntu.com>