Integrate perlio:

Integrate perlio:

[  8290]
Loose the "Loading..." warning.
Another bug in fallback support

[  8288]
Fix .ucm reading - forgot a chr()
Start of .ucm write (for .enc to .ucm)

[  8285]
Start of support of ICU-style .ucm files:
- teach compile how to read a .ucm file
- first guess at how to represent fallbacks in "tries".
- use fallbacks if check == 0
- new return code to indicate we used one.

p4raw-link: @8290 on //depot/perlio: c8991b40a4a3c9ec8efc70a2420a12ff1ce50eb0
p4raw-link: @8288 on //depot/perlio: e0c49a6baed38305536b5d74ba7486451327612c
p4raw-link: @8285 on //depot/perlio: 9b37254de3a0e643859aebea34267588f789f15f

p4raw-id: //depot/perl@8292