TST: Some Stata test datasets do not match the expected version

[cmjcharlton]

A few of the Stata datasets used for testing are not in the format implied by their file names:

• stata4_114.dta appears to actually be saved in 115 format.
• stata9_115.dta appears to actually be saved in 117 format
• stata10_115.dta appears to actually be saved in 117 format

This may result in reduced test coverage for the expected versions.