Editorial: eliminate unsupported "SV of |SourceCharacter|"

We have rules that say the TRV of something is:
 - the SV of the |SourceCharacter| that is that single code point; or
 - the SV of the |SourceCharacter| that is that |HexDigit|.

but there's no definition for the SV of |SourceCharacter|.

We could add such a definition, except that these usages are already odd,
in that they introduce a |SourceCharacter| nonterminal when there isn't one
in the parse tree. So instead, fix that oddity by eliminating the references
to SV and |SourceCharacter|.

And since I'm in the neighborhood,
   The TRV of a |HexDigit| ...
is weird. No other SDO rule is written that way. Change it to:
   The TRV of <emu-grammar>HexDigit :: ....</emu-grammar> ...

spec.html

@@ -11912,7 +11912,7 @@ <h1>Static Semantics: TV and TRV</h1>
             The TRV of <emu-grammar>NotEscapeSequence :: `u` `{` CodePoint [lookahead &lt;! HexDigit] [lookahead != `}`]</emu-grammar> is the sequence consisting of the code unit 0x0075 (LATIN SMALL LETTER U) followed by the code unit 0x007B (LEFT CURLY BRACKET) followed by the code units of the TRV of |CodePoint|.
           </li>
           <li>
-            The TRV of <emu-grammar>DecimalDigit :: one of `0` `1` `2` `3` `4` `5` `6` `7` `8` `9`</emu-grammar> is the SV of the |SourceCharacter| that is that single code point.
+            The TRV of <emu-grammar>DecimalDigit :: one of `0` `1` `2` `3` `4` `5` `6` `7` `8` `9`</emu-grammar> is the UTF16Encoding of the single code point matched by this production.
           </li>
           <li>
             The TRV of <emu-grammar>CharacterEscapeSequence :: SingleEscapeCharacter</emu-grammar> is the TRV of |SingleEscapeCharacter|.
@@ -11921,7 +11921,7 @@ <h1>Static Semantics: TV and TRV</h1>
             The TRV of <emu-grammar>CharacterEscapeSequence :: NonEscapeCharacter</emu-grammar> is the SV of |NonEscapeCharacter|.
           </li>
           <li>
-            The TRV of <emu-grammar>SingleEscapeCharacter :: one of `'` `"` `\` `b` `f` `n` `r` `t` `v`</emu-grammar> is the SV of the |SourceCharacter| that is that single code point.
+            The TRV of <emu-grammar>SingleEscapeCharacter :: one of `'` `"` `\` `b` `f` `n` `r` `t` `v`</emu-grammar> is the UTF16Encoding of the single code point matched by this production.
           </li>
           <li>
             The TRV of <emu-grammar>HexEscapeSequence :: `x` HexDigit HexDigit</emu-grammar> is the sequence consisting of the code unit 0x0078 (LATIN SMALL LETTER X) followed by TRV of the first |HexDigit| followed by the TRV of the second |HexDigit|.
@@ -11942,7 +11942,7 @@ <h1>Static Semantics: TV and TRV</h1>
             The TRV of <emu-grammar>HexDigits :: HexDigits HexDigit</emu-grammar> is the sequence consisting of TRV of |HexDigits| followed by TRV of |HexDigit|.
           </li>
           <li>
-            The TRV of a |HexDigit| is the SV of the |SourceCharacter| that is that |HexDigit|.
+            The TRV of <emu-grammar>HexDigit :: one of `0` `1` `2` `3` `4` `5` `6` `7` `8` `9` `a` `b` `c` `d` `e` `f` `A` `B` `C` `D` `E` `F`</emu-grammar> is the UTF16Encoding of the single code point matched by this production.
           </li>
           <li>
             The TRV of <emu-grammar>LineContinuation :: `\` LineTerminatorSequence</emu-grammar> is the sequence consisting of the code unit 0x005C (REVERSE SOLIDUS) followed by the code units of TRV of |LineTerminatorSequence|.