imfile: Initial implementation of solaris FEN API (without wildcards)
FEN API is used to implement simular event based file
monitoring like with inotify.
This commit provides partial functionality. It supports event-driven
processing of files but does not yet provide wildcard functionality.
Wildscards will be provided by a later commit.
This can be committed as-is because the previous code did also
not provide wildcard support, so this is an improvement for
Solaris in any case.
see also https://github.com/rsyslog/rsyslog/issues/1954
This was not really tested before, and with the new code it turned
out that the expected value was not adjusted when copying the test
from another test file.
Buffer corruption can happen when state is persisted while a partial
line segment of the multi-line message is being held in buffer.
Thanks to Magnus Hyllander for reporting and analyzing this problem.
see also https://github.com/rsyslog/rsyslog/issues/874
