Forbid {�} as a valid expression (#576)

* Forbid {�} as a valid expression

* Drop U+FFFD also from name-char

Author: eemeli

spec/message.abnf

@@ -91,7 +91,7 @@ name-start = ALPHA / "_"
            / %xC0-D6 / %xD8-F6 / %xF8-2FF
            / %x370-37D / %x37F-1FFF / %x200C-200D
            / %x2070-218F / %x2C00-2FEF / %x3001-D7FF
-           / %xF900-FDCF / %xFDF0-FFFD / %x10000-EFFFF
+           / %xF900-FDCF / %xFDF0-FFFC / %x10000-EFFFF
 name-char  = name-start / DIGIT / "-" / "."
            / %xB7 / %x300-36F / %x203F-2040
 

spec/syntax.md

@@ -793,8 +793,8 @@ name-start = ALPHA / "_"
            / %xC0-D6 / %xD8-F6 / %xF8-2FF
            / %x370-37D / %x37F-1FFF / %x200C-200D
            / %x2070-218F / %x2C00-2FEF / %x3001-D7FF
-           / %xF900-FDCF / %xFDF0-FFFD / %x10000-EFFFF
-name-char  = name-start / DIGIT / "-" / "." / ":"
+           / %xF900-FDCF / %xFDF0-FFFC / %x10000-EFFFF
+name-char  = name-start / DIGIT / "-" / "."
            / %xB7 / %x300-36F / %x203F-2040
 ```