Merge Notation subsections into Notation

Author: Havvy

src/SUMMARY.md

@@ -3,8 +3,6 @@
 [Introduction](introduction.md)
 
 - [Notation](notation.md)
-    - [Unicode productions](unicode-productions.md)
-    - [String table productions](string-table-productions.md)
 
 - [Lexical structure](lexical-structure.md)
     - [Input format](input-format.md)

src/notation.md

@@ -1 +1,29 @@
 # Notation
+
+## Unicode productions
+
+A few productions in Rust's grammar permit Unicode code points outside the
+ASCII range. We define these productions in terms of character properties
+specified in the Unicode standard, rather than in terms of ASCII-range code
+points. The grammar has a [Special Unicode Productions][unicodeproductions]
+section that lists these productions.
+
+## String table productions
+
+Some rules in the grammar — notably [unary
+operators], [binary operators], and [keywords][keywords] — are
+given in a simplified form: as a listing of a table of unquoted, printable
+whitespace-separated strings. These cases form a subset of the rules regarding
+the [token][tokens] rule, and are assumed to be the result of a
+lexical-analysis phase feeding the parser, driven by a DFA, operating over the
+disjunction of all such string table entries.
+
+When such a string enclosed in double-quotes (`"`) occurs inside the grammar,
+it is an implicit reference to a single member of such a string table
+production. See [tokens] for more information.
+
+[unicodeproductions]: ../grammar.html#special-unicode-productions
+[binary operators]: expressions/operator-expr.html#arithmetic-and-logical-binary-operators
+[keywords]: keywords.html
+[tokens]: tokens.html
+[unary operators]: expressions/operator-expr.html#borrow-operators