Capitalised functions marked as incorrect when "allow unknown function names" is off

[georgestagg]

Create a mathematical expression part where the answer is something like e^(-x). When "Allow unknown function names" is on:

• exp(-x) is marked as correct
• Exp(-x) is marked as correct

But, when "Allow unknown function names" is off:

• exp(-x) is marked as correct
• Exp(-x) is marked as incorrect

I would expect "Exp" to be correct either way.

[christianp]

Thanks for spotting this. The expand_juxtapositions routine was case-sensitive, which it shouldn't be.