Added two missing roundtrip case folding tests.

UTF-8 case folding hacks to deal with U+0130, U+0131, U+017f and U+01fbe since these doesn't have any roundtrip compatible mappings nor have case folds into codepoins with the same UTF-8 length. They map to other characters in other blocks.

IPRT/RTCString: fix find method, add testcase

RTCString::join: Optimization.

iprt-cpp: fix RTCString::join when the list contains just one item

IPRT-C++: iprt::list -> RTCList; iprt::mtlist -> RTCMTList

iprt::MiniString -> RTCString.

IPRT: add join/split and + operators to the string class

IPRT: another ministring testcase

IPRT: fix rare crash in MiniString::substr(); rename substr() to substrCP() and add a substr that operates on bytes, not codepoints; more to come

iprt/cpp/ministring.h: Changed the substring constructors to match std::string. As I feared, this caused some minor issues with the format+va_list constructor, fortunately it's only when passing a_cchSrc=0. While at it, I've added the one missing std::string constructor, the repeat character constructor.

tstIprtMiniString.cpp: NULL construction and assignment tests.

now it's right. added tests to prove it.

iprt::MiniString: Fixed bug in compare("") and equals("") caused by m_psz=NULL when m_cch=0 and RTStr[I]Cmp regarding NULL and "" as different things. Added format+va_list constructor.

iprt/cpp/ministring: Added printf and printfV methods.

iprt:ministring: Added the java-style equals() and equalsIgnoreCase() as equals() can optimize the comparison by first checking if the length is the same (compare() cannot as it needs to determin the ordering). Added appendCodePoint() for UTF-8. Fixed the incorrect assumption in toUpper and toLower that the string length remained unchanged - the string might shrink as the folded code points may have a shorter encoding. Added testcase that verifies that a code point will not grow during folding and that have a stable encoding length after it has been changed in a folding.