- add yycc_char8_t and yycc_u8string in code to indicate explicit utf8 char type and string. it also has a polyfill if compiler and library do not support utf8 char type.
- refactor the whole encoding helper. allow converting string with embedded NUL. but not tested.
- add dialog parameter class for dialog helper. prepare to write real dialog popup function.
- refactor file filters class in dialog helper to make it no const syntax conflict.
- improve windows header import prefix and suffix header. remove the barrier limiting headers only can be imported once. fix define preprocessor usage bug.
- move crt warning and errors macro from project settings to internal headers.
- copy IronPad as ExceptionHandler but not adapted to this project.
