add trx_TrxId creator member fuction test code.
add trx_TrxId.cpp to trx/makefile.
change data type name.
	- trx_Usn => usn_t
	- trx_Lsn => lsn_t

prefix is not used for class.
	- ex) trx_TrxId is incorrect. TrxId is correct name.