Proposal: Add UErrorCode to ucurr_get* (JB#3399)

Affects: ICU4C 3.0

Bug: #3399
http://www.jtcsv.com/cgibin/icu-bugs?findid=3399

NumberFormat:
------------
The following @stable API:

    void setCurrency(const UChar* theCurrency);

will be marked @deprecated as of 3.0 in favor of the new API: 

    void setCurrency(const UChar* theCurrency, UErrorCode& ec);
 
These will be inherited by DecimalFormat.


ucurr.h:
-------
The following @draft API

    int32_t ucurr_getDefaultFractionDigits(const UChar* currency);

    double ucurr_getRoundingIncrement(const UChar* currency););

will gain a UErrorCode* parameter and become:

    int32_t ucurr_getDefaultFractionDigits(const UChar* currency,
                                           UErrorCode* ec);

    double ucurr_getRoundingIncrement(const UChar* currency);
                                      UErrorCode* ec);

[Alan S Liu/San Jose/IBM@IBMUS; [email protected];; IBM Globalization; 
5600 Cottle Road; San Jose, CA 95193;; (408) 256-3155]