Add flags to page release, respect WT_READ_NO_GEN to avoid forced eviction.

refs #1128, #1134
include/btree.i:956:15: error: 'flags' may be used uninitialized in this function
whitespace
__wt_page_release doesn't look at the WT_READ_CACHE flag.
Split the WT_READ_NO_GEN flag to clarify: sometimes we mean "this read should not bump the read generation" and sometimes we mean "this read should not cause pages to be evicted".
__wt_page_release() only cares about WT_READ_NO_EVICT, don't pass
other flags in.
Merge branch 'develop' into page-release-flags
Switch a page-release call from WT_READ_NO_GEN to WT_READ_NO_EVICT.
whitespace typo
__wt_page_release doesn't look at WT_READ_NO_GEN, don't pass it in.
Merge pull request #1160 from wiredtiger/page-release-flags

Add flags to page release, respect WT_READ_NO_GEN to avoid forced eviction