Try not marking icudt symbols as __declspec(dllimport)

We were getting build errors:

FAILED: D:\Python27\python.exe gyp-win-tool link-wrapper environment.x86 link.exe /nologo /OUT:tld_cleanup.exe /PDB:tld_cleanup.exe.pdb @tld_cleanup.exe.rsp && D:\Python27\python.exe gyp-win-tool manifest-wrapper environment.x86 cmd /c if exist tld_cleanup.exe.manifest del tld_cleanup.exe.manifest && D:\Python27\python.exe gyp-win-tool manifest-wrapper environment.x86 mt.exe -nologo -manifest obj\net\tld_cleanup.tld_cleanup.exe.intermediate.manifest -out:tld_cleanup.exe.manifest
icuuc.lib(icuuc.udata.obj) : error LNK2001: unresolved external symbol __imp__icudt46_dat