[REVIEW 3-6] Prevent exporting raw field names in pivot table to ODS

Hi there,

I'd like

https://gerrit.libreoffice.org/gitweb?p=core.git;a=commitdiff;h=fe0ef1b2f13d1c2cc8e4f777911c158390183053

cherry-picked to 3-6 to prevent us from exporting any internal field 
names in pivot table to ODS.

Background

Our pivot table code internally appends '*' character to a duplicate 
field name, because we require that each field name be unique.  The 
decision was not mine but it had been done this way historically.

Unfortunately, this scheme has a big drawback that, if the real field 
name ends with '*', it would cause a catastrophic result.  To make 
matters worse, the document that caused a crash earlier in this bug report

https://bugs.freedesktop.org/show_bug.cgi?id=54303

contained a field whose name was just '*'!

During the 3.6 cycle, I had spent a great deal to isolate the parts of 
the code that adds and removes these '*' from the real field name, with 
the intention of changing this suffix character from '*' to something 
else (probably one that's outside the printable range).

So, it's very important that we prevent these characters from being 
exported into ODS.

Kohei

--
Kohei Yoshida, LibreOffice hacker, Calc