unbroken dev/icu in current

[Rodrigo OSORIO]

Hi,

The port dev/icu fails to build in current due to an lock issue
caused by the use of threads api. 
Disabling threads for icu in current solves the problem  and the port 
can be build successfully and AFAIK this unbroke some of the ports who 
depends on icu. 

I don't know if this can be an acceptable short-term workaround for this
por ?

 Regards,
- rodrigo