Check that handles are not being walked by eviction before discarding.

refs #1497
Insulate against language-specific sort order in s_win.
Remove the SET/CLEAR_BTREE_IN_SESSION macros: now we have WT_WITH_DHANDLE, they don't make much sense.
Skip test_schema03.py on Window since rlimits are unix specific
Add __wt_getenv to workaround caching in MSVC CRT's getenv implementation.
Merge pull request #1502 from markbenvenuto/win_test_schema03

Skip test_schema03.py on Window since rlimits are unix specific
Merge pull request #1504 from markbenvenuto/wt_getenv

Add __wt_getenv to workaround caching in MSVC CRT's getenv implementation
Merge branch 'develop' into evict-trickle