Change the format of TRX_IDs in INFORMATION_SCHEMA tables from DEC to
HEX.

The current TRX_IDs are hard to remember and track down: 426355, 428466,
428566, etc.

In HEX:
* there are less "digits", the strings are shorter;
* since there are 16 instead of 10 "digits", the chance of having
  repeating ones are smaller.

The above look like 68173, 689B2, 68A16 in HEX.

Discussed with:	Ken
Approved by:	Heikki (via IM)