Switch BackgroundIframe test from java applet to PDF,
since the java applet wasn't loading correctly.

(cherry picked from dijit fb0203a01d0869ad5278c5675d986698209a7c24)
Workaround iOS bug where clicking Menu can focus/click an input/button behind it.
Fixes #17816.

Cherry picked from dijit:

- e9a09987211acd8b3b59ed2359b4d21fef099913
- 7efe39728726534c59abc5e82afcff4e3c1ade8c
- af2b3c2d13a83aaf0a217eac99e674a1ae253f96
Update source code comment and fix typo.
Cherry picked from dijit b7d6d40767ca6aca9d5b2d228f1a42447cf6407a.
CSS position properties in popup._repositionAll() are now treated as floats instead of ints, fixes #17990.

(cherry picked from dijit 8c920c8b6da7d015c19c74049387f82af1611ef7)
KeyNav Don't treat SPACE as the start of a keyboard search.