[PATCH] Fix strange behavior when summing rows/columns containing strings

Hi everybody!

Attached patch file fixes the problem with strange behavior observed
when summing rows/columns containing strings. I have chosen the
simplest (and IMO robust) approach - now AbiWord simply skips
rows/cells which doesn't contain valid double values. Contrary to the
strtod() function, only cells containing valid double values (in
standard or scientific notation) followed by whitespaces are summed.
Valid values are, in this case, for example:

-"8e1 ";
-"-80";

whereas invalid ones are:

-"8e1 20";
-"C3PO";
-"4t" - strtod() function converts it to 4.000, but we don't want to sum it;

This is standard convention used in most of word processors.

On the other hand, I have researched the possibility to enable
currency and unit symbols for cells. Current implementation of this
feature is rather obfuscated and locale-agnostic, which is not very
good. It also seems that somebody disabled it, but the whole bunch of
if statements is still evaluated. I can clear this.

I would be very grateful for any feedback concerning my patch.

Regards,
Rafal Kulaga