Fix improper check for mbrlen/mblen, to deal with the configuration failure for Android below API level 26

[zjyhjqs]

(I know this is not a GitHub project. But my application for JIRA account hasn't been replied yet.)

The usage place (IconvLCPTranscoder::calcRequiredSize) will check the existence of ::mbrlen first. If not then use the ::mblen as alternative.

xerces-c/src/xercesc/util/Transcoders/Iconv/IconvTransService.cpp

Lines 237 to 241 in 5fe4f4b

	#if HAVE_MBRLEN
	int l=::mbrlen( src, MB_CUR_MAX, &st );
	#else
	int l=::mblen( src, MB_CUR_MAX );
	#endif

NDK doesn't provide the implementation of ::mblen below API level 26. Only checks HAVE_MBLEN would consequence to configuration failure.