disallowed referencing variables from inside secondary index functions (c.f. Issue #718)
made `between` abort earlier if its left key is greater than its right key (c.f. Issue #614)
Removed MCHECK from src/build.mk, errors.hpp/cc.
Removed MCHECK from mk/way/default.mk.
Moved terms implementations to .cc files.
Moved term_walker_t implementation to term_walker.cc.
Removed unused types broken_client_exc_t and bad_query_exc_t.
Removed unused meta_check function.
Got rid of rdb_protocol/pretty_print.hpp.
Improved NaN Checking.
Improved groupby error message (c.f. Issue #525).
updated yaml docs to say aggregator
Merge branch 'next' into sam_etc_deheaderize

Conflicts:
	src/rdb_protocol/term_walker.hpp
Moved transform_visitors.hpp implementations to cc file.
Merge branch 'next' into sam_etc_no_mcheck
Merge branch 'next' into sam_etc_deheaderize
added comment and changed to private inheritance for special_var_shadower_t
Merge branch '614_make_tests_run_in_debug' into next
merge fix
Merge branch '767_better_nan_checking' into next