Some methods implemented as 'inline' are not declared 'inline'. This triggers compilation warnings when building ICU for Windows with clang++. For example:
icu/icu4c/source/common/unicode/unistr.h:4604:16: 'icu_63::UnicodeString::setTo' redeclared inline; 'dllimport' attribute ignored.
The patch also removes 'dllimport' attributes for inline methods, as they would be ignored and trigger the warning:
icu/icu4c/source/common/unicode/unistr.h:1935:10: 'dllimport' attribute ignored on inline function
Patch attached fixing the warnings.