More relaxed parsing of preprocessed qstr header
The original parsing would error out on any C declarations that are not typedefs or extern variables. This limits what can go in mpconfig.h and mpconfigport.h, as they are included in qstr.h. For instance even a function declaration would be rejected and including system headers is a complete no-go. That seems too limiting for a global config header, so makeqstrdata now ignores everything that does not match a qstr definition.