Cast user pref strings.

[Mictronics]

Fixes the following build errors when user preference strings are numerical only. e.g. short name is 4 numbers.

error: invalid conversion from 'int' to 'const char*' [-fpermissive]
error: initializer fails to determine size of 'slipstreamTZString'
error: array must be initialized with a brace-enclosed initializer

[fifieldt]

Good catch, thanks.