C++: Step 4 of the std::string transition. Remove C style string lambda support due to limitations of std::function. std::function due to its template definition cannot differentiate parameters. This causes std::function parameters to be indistiguishable despite different signatures. Use the C style function pointer instead if you want C style strings, not lambdas. Convert KeyPress lambda to use std::string, this was missed in the last commit.

# Set these here to change the version for all platforms
DW_MAJOR_VERSION=3
DW_MINOR_VERSION=3