#1587 scriptedwizard : ensure header guard macro is a valid C identifier

[Christo]

When selecting File->New->File->C/C++ header, in the wizard, the header guard is generated based on file name. But the header guard will cause compilation error if filename contains characters such as hyphen. Attaching patch to ensure the generated header guard obeys C identifier requirements.

[Miguel Gimenez]

Applied in [r13788], thank you.