If the percentage of dirty pages in the buffer pool
exceeds innodb_max_dirty_pages_pct (set by the user)
then we flush the pages.If user sets 
innodb_max_dirty_pages_pct=0,then the flushing mechanism
will not kick in unless the percentage of dirty pages
reaches at least 1%.For huge buffer pools even 1% of the
buffer pool can be a huge number.

FIX
---

Flush the dirty pages in buffer pool if percentage of dirty
pages equals innodb_max_dirty_pages_pct or exceeds it. We have
changed the innodb_max_dirty_pages_pct and 
innodb_max_dirty_pages_pct_lwm to double value,so that user
can fine tune the percentage of dirty pages in the buffer pool.

[ Approved by vasil #rb4778 ]