#74 narrow type in else block of switch
oops, fix npe
for #74 narrow type in else block of if
allow !nonempty and !exists conditions, useful in conjunction with #74
Merge branch 'master' into 74
fix else clause node spans
check for ==
for @FroMage
Merge branch 'master' into 74
fix impl of #74, don't use subtraction
tests for #74
small fix + test for #74
spec for #74
ooops, forgot important limit in spec for #74
fix bugs and add test for negated conditions for #74
Merge branch 'master' into 74
Merge branch 'master' into 74
Merge branch 'master' into 74, resolving conflicts between else clause narrowing and inline if/switch

Conflicts:
	Ceylon.nodes
oops, forgot to commit these as part of @6cc01f652267d4913399336858ae01917303a0a5
I prefer this fix to #1143, but thanks anyway @lucaswerkmeister