Support kit: Fixed issues in BString unit tests

1: Changed CPPUNIT_ASSERT -> CPPUNIT_ASSERT_EQUAL
2: Fixed coding style: Added two lines after including libraries, maintained 80 characters(MAX) in each line and space at comment start
3: Fixed the failure for "BString::Search" test "i != 0 by chaning the testing method(StartsWith->IStartsWith) and changed the string to be searched(sT->st)

Change-Id: I1237d1f2d0e3af7757963cc940bae929f487f088

BString: fix Split() for multiple characters separators...

as suggested by Janus in #14045. Thanks!
* add a unit test for BString::Split().