Recent definitions are using non standard Symbol naming

[RussBerg]

Not sure how I missed this until now but the files listed below are using symbol names that are not using lower camel case as defined in the documentation for a symbols table:

• NXapm
• NXellipsometry
• NXmpes
• NXoptical_spectroscopy
• NXraman
• NXstress

Using a symbol from NXapm as an example, n_ht should be nHt, etc.