removing Hmisc dependency

same result from foreign by passing to.data.frame = TRUE to read.spss; lost datevars functionality, which operates by default for Stata files through convert.dates = TRUE in read.dta; won same underscore behaviour (spss.get converts them for R < 1.9, read.dta can but abstains); recoding qogdata to use read.spss, using to.data.frame = TRUE, plus coding convert.dates=T option and convert.underscores=T option for SPSS.