Add glibc version and effective locale to the Web UI

When debugging utf8 mode string functions, it's essential to know the effective Unicode version and locale. The Unicode standard version can be deduced from the glibc version which can be got by command "ldd --version". We need to find a programmatic way to get it.

The effective locale is already logged here:
https://github.com/apache/impala/blob/ba4cb95b6251911fa9e057cea1cb37958d339fed/be/src/common/init.cc#L406
We just need to show it in impalad's Web UI as well.