8186072: dll_build_name returns true even if file is missing.
Summary: Split dll_build_name into two functions and consolidate to os.cpp file.
Reviewed-by: stuefe, dholmes
8185624: G1HeapVerifier's VerifyRootsClosure prints important information on info log level
Summary: Fix logging of broken oop to error log level instead of info log level
Reviewed-by: mgerdin, tschatzl
Contributed-by: muthusamy.chinnathambi@oracle.com