partial fix to register window performance problem.

[Linas Vepstas]

Log Message:
-----------
partial fix to register window performance problem.
See http://bugzilla.gnome.org/show_bug.cgi?id=120028 for details.
This patch can speed transaction commit significantly for
systems with a large number of accounts.  Initial register open 
remains slow.

Tags:
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gnucash-1-8-branch

Modified Files:
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    gnucash/src/register/ledger-core:
        split-register-load.c