audio/ncmpcpp: unbreak with ICU 61

In file included from screens/browser.cpp:27:
In file included from ./screens/browser.h:26:
./regex_filter.h:45:22: error: unknown type name 'UnicodeString'; did you mean 'icu::UnicodeString'?

static void convert(UnicodeString &s)
                    ^~~~~~~~~~~~~
                    icu::UnicodeString

/usr/local/include/unicode/unistr.h:286:20: note: 'icu::UnicodeString' declared here
class U_COMMON_API UnicodeString : public Replaceable

^

In file included from screens/browser.cpp:27:
In file included from ./screens/browser.h:26:
./regex_filter.h:61:9: error: unknown type name 'Transliterator'; did you mean 'UTransliterator'?

static Transliterator *m_converter;
       ^~~~~~~~~~~~~~
       UTransliterator

/usr/local/include/unicode/utrans.h:70:15: note: 'UTransliterator' declared here
typedef void* UTransliterator;

^

In file included from screens/browser.cpp:27:
In file included from ./screens/browser.h:26:
./regex_filter.h:49:4: error: unknown type name 'ErrorCode'; did you mean 'UErrorCode'?

ErrorCode result;
^~~~~~~~~
UErrorCode

/usr/local/include/unicode/utypes.h:663:3: note: 'UErrorCode' declared here
} UErrorCode;

^

In file included from screens/browser.cpp:27:
In file included from ./screens/browser.h:26:
./regex_filter.h:50:18: error: use of undeclared identifier 'Transliterator'; did you mean 'icu::Transliterator'?

m_converter = Transliterator::createInstance(
              ^~~~~~~~~~~~~~
              icu::Transliterator

/usr/local/include/unicode/translit.h:243:18: note: 'icu::Transliterator' declared here
class U_I18N_API Transliterator : public UObject {

^

In file included from screens/browser.cpp:27:
In file included from ./screens/browser.h:26:
./regex_filter.h:50:18: error: assigning to 'UTransliterator *' (aka 'void **') from incompatible type 'icu::Transliterator *'

m_converter = Transliterator::createInstance(
              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

./regex_filter.h:52:14: error: member reference base type 'UErrorCode' is not a structure or union

if (result.isFailure())
    ~~~~~~^~~~~~~~~~

./regex_filter.h:55:26: error: member reference base type 'UErrorCode' is not a structure or union

+ std::string(result.errorName()));
              ~~~~~~^~~~~~~~~~

./regex_filter.h:57:14: error: member reference base type 'UTransliterator' (aka 'void *') is not a structure or union

m_converter->transliterate(s);
~~~~~~~~~~~^ ~~~~~~~~~~~~~

./regex_filter.h:64:1: error: unknown type name 'Transliterator'; did you mean 'UTransliterator'?
Transliterator *StripDiacritics::m_converter;
^~~~~~~~~~~~~~
UTransliterator
/usr/local/include/unicode/utrans.h:70:15: note: 'UTransliterator' declared here
typedef void* UTransliterator;

^

In file included from screens/browser.cpp:27:
In file included from ./screens/browser.h:26:
./regex_filter.h:102:14: error: use of undeclared identifier 'UnicodeString'; did you mean 'icu::UnicodeString'?

auto us = UnicodeString::fromUTF8(
          ^~~~~~~~~~~~~
          icu::UnicodeString

/usr/local/include/unicode/unistr.h:286:20: note: 'icu::UnicodeString' declared here
class U_COMMON_API UnicodeString : public Replaceable

^

In file included from screens/browser.cpp:27:
In file included from ./screens/browser.h:26:
./regex_filter.h:103:5: error: use of undeclared identifier 'StringPiece'

StringPiece(convertString<char, CharT>::apply(s)));
^

screens/browser.cpp:737:16: note: in instantiation of function template specialization 'Regex::search<char>' requested here

return Regex::search(itemToString(item), rx, Config.ignore_diacritics);
              ^

https://ssl.icu-project.org/trac/changeset/40705

PR: 227042
Reported by: antoine (via exp-run)