New InternalStatistics
allow to configure the maximum effective interval between attempts to read data by plugins
rename option MaxEffectiveInterval -> MaxReadInterval
nb_values missing in types.db; renaming as cache_size
document MaxReadInterval option
renamed the option to CollectInternalStats; renamed 'internal' to 'collectd'; no more lock when not recording internal stats
parse option MaxReadInterval in the plugin_init_all()
src/configfile.c: Use cf_util_get_cdtime() to parse the "Interval" settings.
src/configfile.[ch]: Implement global_option_get_time().
src/plugin.c: Parse "MaxReadInterval" with global_option_get_time().
Merge branch 'pr-713'
Merge remote-tracking branch 'origin/pr/691'
improve CollectInternalStats's documentation
RPM specfile: remove duplicate modbus block
RPM specfile: remove macro accidentally re-added when handling merge conflict
RPM specfile: remove define accidentally re-added when handling merge conflict
RPM specfile: add missing %files section for modbus plugin

complement to a781eb2c5
RPM specfile: support for RHEL7
RPM specfile: fix bogus dates

modern rpmbuild versions appear to be more strict on this point.
RPM specfile: enable netlink plugin on RHEL > 5