switch to proper merging of no_nul annotation, and fix translation
test for Dir#glob behaviour in presence of null-bytes in the arguments
add test for behaviour if a nul-byte string is added to LOAD_PATH
add tests for  element coercion
move raising of ArgumentError into space
add tests for null-bytes in exec call
remove assert_str0's
remove remaining uses of assert_str0
remove confusing comment
nits
Merge pull request #502 from topazproject/tim/handle-no_nul-strings

Switch to proper merging of no_nul annotation, and fix translation
Merge remote-tracking branch 'upstream/master' into mbh/buffered-diskio-stream
Still not translating.

This makes a few adjustments to clean up the summary diff.  I fought
far too long with the annotater wrt strings with NULLs.  Needs help.