[plt-scheme] Fixes for some typos in v4 documentation

Index: namespaces.scrbl
===================================================================
--- namespaces.scrbl	(revision 8366)
+++ namespaces.scrbl	(working copy)
@@ -76,7 +76,7 @@
 which @scheme[scheme] is built.
 
 To make a namespace useful, some modules much be @deftech{attached}
-from an existing namespace. Attaching a module adjust the mapping of
+from an existing namespace. Attaching a module adjusts the mapping of
 module names to instances by transitively copying entries (the module
 and all its imports) from an existing namespace's mapping. Normally,
 instead of just attaching the primitive modules---whose names and
@@ -106,7 +106,7 @@
 ]
 
 Note that the @scheme[parameterize] of @scheme[current-namespace] does
-not affect the meaning of identifier like @scheme[namespace-require]
+not affect the meaning of identifiers like @scheme[namespace-require]
 within the @scheme[parameterize] body. Those identifiers obtain their
 meaning from the enclosing context (probably a module). Only
 expressions that are dynamic with respect to this code, such as the
Index: contracts-gotchas.scrbl
===================================================================
--- contracts-gotchas.scrbl	(revision 8366)
+++ contracts-gotchas.scrbl	(working copy)
@@ -38,7 +38,7 @@
 inside the module @scheme[x]).
 
 To work around this, export accessor functions, rather than
-exporting the function directly, like this:
+exporting the variable directly, like this:
 
 @schememod[
 scheme
Index: performance.scrbl
===================================================================
--- performance.scrbl	(revision 8366)
+++ performance.scrbl	(working copy)
@@ -35,8 +35,8 @@
 1 (y)))] is compiled the same as the constant @scheme[5].
 
 On some platforms, bytecode is further compiled to native code via a
- at deftech{jut-in-time} or @deftech{JIT} compiler. The @tech{JIT}
-compiler substantially speed programs that execute tight loops,
+ at deftech{just-in-time} or @deftech{JIT} compiler. The @tech{JIT}
+compiler substantially speeds programs that execute tight loops,
 arithmetic on small integers, and arithmetic on inexact real
 numbers. Currently, @tech{JIT} compilation is supported for x86,
 x86_64 (a.k.a. AMD64), and 32-bit PowerPC processors. The @tech{JIT}
@@ -59,7 +59,7 @@
 The module system aids optimization by helping to ensure that
 identifiers have the usual bindings. That is, the @scheme[+] provided
 by @schememodname[scheme/base] can be recognized by the compiler and
-inlined, which is especially imported for @tech{JIT}-compiled code.
+inlined, which is especially important for @tech{JIT}-compiled code.
 In contrast, in a traditional interactive Scheme system, the top-level
 @scheme[+] binding might be redefined, so the compiler cannot assume a
 fixed @scheme[+] binding (unless special flags or declarations
@@ -82,7 +82,7 @@
 @secref["module-set"] for more information.
 
 Currently, the compiler does not attempt to inline or propagate
-constant across module boundary, except for exports of the built-in
+constants across module boundaries, except for exports of the built-in
 modules (such as the one that originally provides @scheme[+]).
 
 The later section @secref["letrec-performance"] provides some
Index: contracts-structure.scrbl
===================================================================
--- contracts-structure.scrbl	(revision 8366)
+++ contracts-structure.scrbl	(working copy)
@@ -247,7 +247,7 @@
 ]
 
 In general, each use of @scheme[node/dc] must name the
-fields and then specify contracts for each fields. In the
+fields and then specify contracts for each field. In the
 above, the @scheme[val] field is a contract that accepts
 values between @scheme[low] and @scheme[high].
 The @scheme[left] and @scheme[right] fields are
Index: io.scrbl
===================================================================
--- io.scrbl	(revision 8366)
+++ io.scrbl	(working copy)
@@ -304,7 +304,7 @@
 that can be @scheme[serialize]d to a value that can be printed using
 @scheme[write] and restored via @scheme[read]. The @scheme[serialize]d
 result can be @scheme[deserialize]d to get back an instance of the
-original structure type. The serialization form an functions are
+original structure type. The serialization form and functions are
 provided by the @schememodname[scheme/serialize] library.
 
 @examples[

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