Get specific about what RESOLVE() means, and link usage of it to the place

where it is defined.

Fixes #144.

doc/tables.qbk

@@ -18,7 +18,7 @@ itself be used as a parser; it must be called.  In the table below:
   "`char`");
 
 * _RES_ is a notional macro that expands to the resolution of parse argument
-  or evaluation of a parse predicate;
+  or evaluation of a parse predicate (see _parsers_uses_);
 
 * "`_RES_np_(pred) == true`" is a shorthand notation for "`_RES_np_(pred)` is
   contextually convertible to `bool` and `true`"; likewise for `false`;
@@ -406,7 +406,7 @@ This table summarizes the attributes generated for all _Parser_ parsers.  In
 the table below:
 
 * _RES_ is a notional macro that expands to the resolution of parse argument
-or evaluation of a parse predicate, and
+or evaluation of a parse predicate (see _parsers_uses_); and
 
 * `x` and `y` represent arbitrary objects.
 

doc/tutorial.qbk

@@ -1080,7 +1080,9 @@ This can also be a lambda.  For example:
 
 The operation that produces a value from a parse argument, which may be a
 value or a callable taking a parse context argument, is referred to as
-/resolving/ the parse argument.
+/resolving/ the parse argument.  If a parse argument `arg` can be called with
+the current context, then the resolved value of `arg` is `arg(ctx)`;
+otherwise, the resolved value is just `arg`.
 
 Some callable parsers take a /parse predicate/.  A parse predicate is not
 quite the same as a parse argument, because it must be a callable object, and
@@ -1100,6 +1102,9 @@ This may of course be a lambda:
 
     [](auto & ctx) { return _attr(ctx) == 3; }
 
+The notional macro _RES_ expands to the result of resolving a parse argument
+or parse predicate.  You'll see it used in the rest of the documentation.
+
 An example of how parse arguments are used:
 
     namespace bp = boost::parser;