Small English usage nits.

Doc/lib/liblinecache.tex

 \section{\module{linecache} ---
-         Treat files like lists of lines}
+         Random access to text lines}
 
 \declaremodule{standard}{linecache}
 \sectionauthor{Moshe Zadka}{mzadka@geocities.com}
-\modulesynopsis{This module treats files like random-access lists of lines.}
+\modulesynopsis{This module provides random access to individual lines
+                from text files.}
 
 
 The \module{linecache} module allows one to get any line from any file,
 while attempting to optimize internally, using a cache, the common case
-where many lines are read from a file.
+where many lines are read from a single file.  This is used by the
+\refmodule{traceback} module to retrieve source lines for inclusion in 
+the formatted traceback.
 
 The \module{linecache} module defines the following functions:
 
@@ -17,19 +20,19 @@ Get line \var{lineno} from file named \var{filename}. This function
 will never throw an exception --- it will return \code{''} on errors.
 
 If a file named \var{filename} is not found, the function will look
-for it in the module search path.
+for it in the module\indexiii{module}{search}{path} search path,
+\code{sys.path}.
 \end{funcdesc}
 
 \begin{funcdesc}{clearcache}{}
-Clear the cache. You might want to use this function if you know that
-you do not need to read lines from many of files you already read from
-using this module.
+Clear the cache.  Use this function if you know that you do not need
+to read lines from many of files you already read from using this
+module.
 \end{funcdesc}
 
 \begin{funcdesc}{checkcache}{}
-Check the cache is still valid. You might want to use this function if
-you suspect that files you read from using this module might have
-changed.
+Check the cache for validity.  Use this function if files in the cache 
+may have changed on disk, and you require the updated version.
 \end{funcdesc}
 
 Example: