Problem exporting strings starting with an equals sign

[AzzaAzza69]

This fix may not work properly when writing out formula's but as I am only exporting data, it works for me!

in the writeCell( function ... } elseif (/* modified AzzaAzza69 /$num_format_type!='n_string'/ AzzaAzza69*/ && is_string($value) && $value[0]=='='){ ...