Guile-1.6 doesn't allow string->symbol on a symbol (bug #131201).

[Derek Atkins]

Log Message:
-----------
Guile-1.6 doesn't allow string->symbol on a symbol (bug #131201).

	* src/report/locale-specific/us/taxtxf.scm: guile-1.6 complains
	  about string->symbol when passed a symbol.  Fixes #131201
	  Also add some code to handle accounts that are expected to
	  have parents but do not (also described in #131201).

Tags:
----
gnucash-1-8-branch

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/report/locale-specific/us:
        taxtxf.scm