Better "carry" flag to not overrun a signed 64-bit int (#114980).

[Derek Atkins]

Log Message:
-----------
Better "carry" flag to not overrun a signed 64-bit int (#114980).

	* src/engine/gnc-numeric.c: small change to the 128-bit math
	  routines to actually mark a 'carry bit' to denote numbers
	  >= 2^63 to fix bug #144980.

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/engine:
        gnc-numeric.c