Improved checks for scanf %lld and %qd as per gc-devel mail.

[Derek Atkins]

Log Message:
-----------
Improved checks for scanf %lld and %qd as per gc-devel mail.

	* acinclude.m4: create a SCANF_QD_CHECK and make sure both
	  that and SCANF_LLD_CHECK are "long long" constant-safe 
	* configure.in: use the new SCANF_QD_CHECK and use it
	  earlier in the configuration.

Modified Files:
--------------
    gnucash:
        ChangeLog
        acinclude.m4
        configure.in