Fix quoting in CI definition

Quote the command introduced in
6a9992b9ea35eb67a9dab1a9a5a218c0a57c2efc.
Fix #1239: Don't assume in ExtJSEnv that VM supports require
Merge pull request #1250 from gzm0/improve-partest

Fix quoting in CI definition
Merge pull request #1251 from gzm0/no-require

Fix #1239: Don't assume in ExtJSEnv that VM supports require
Fix #1252: Missing asInstanceOf's/unbox'es in scalajsenv.js.

Only one was really a danger, i.e., the result of charCodeAt()
in charSequenceCharAt() with an out-of-bounds index. The others,
being calls to methods of primitive data types, are hardly a
problem, because the implementations cannot return wrong results.
(Of course, they could be overwritten by an evil user, so it's
better to check them.)
Merge pull request #1253 from sjrd/issue-1252

Fix #1252: Missing asInstanceOf's/unbox'es in scalajsenv.js.