This commit refactors all functions so they have consistent behavior for the space-as-plus encoding option.
- any_params_iter objects store and apply the appropriate option when measuring and copying
- when the option is enabled, encoding functions encode space-as-plus and plus as %2B regardless of the charset
- normalization and comparison algorithms take into consideration special query chars whose meaning changes depending on encoding
- all params_view objects created with default options enable space-as-plus encoding
fix#903
