Improve wording in pg_dump compression docs

A couple minor corrections in pg_dump comments and docs, related to the
recently introduced compression API.

Reported-by: Justin Pryzby
Discussion: https://postgr.es/m/20230227044910.GO1653@telsasoft.com

Author: tvondra

doc/src/sgml/ref/pg_dump.sgml

@@ -331,7 +331,7 @@ PostgreSQL documentation
            can read. A directory format archive can be manipulated with
            standard Unix tools; for example, files in an uncompressed archive
            can be compressed with the <application>gzip</application> or
-           <application>lz4</application>tool.
+           <application>lz4</application> tools.
            This format is compressed by default using <literal>gzip</literal>
            and also supports parallel dumps.
           </para>
@@ -654,8 +654,8 @@ PostgreSQL documentation
       <listitem>
        <para>
         Specify the compression method and/or the compression level to use.
-        The compression method can be set to <literal>gzip</literal> or
-        <literal>lz4</literal> or <literal>none</literal> for no compression.
+        The compression method can be set to <literal>gzip</literal>,
+        <literal>lz4</literal>, or <literal>none</literal> for no compression.
         A compression detail string can optionally be specified.  If the
         detail string is an integer, it specifies the compression level.
         Otherwise, it should be a comma-separated list of items, each of the

src/bin/pg_dump/compress_io.h

@@ -172,7 +172,7 @@ struct CompressFileHandle
 extern CompressFileHandle *InitCompressFileHandle(const pg_compress_specification compression_spec);
 
 /*
- * Initialize a compress file stream. Deffer the compression algorithm
+ * Initialize a compress file stream. Infer the compression algorithm
  * from 'path', either by examining its suffix or by appending the supported
  * suffixes in 'path'.
  */

src/bin/pg_dump/compress_lz4.c

@@ -161,8 +161,8 @@ typedef struct LZ4File
 } LZ4File;
 
 /*
- * LZ4 equivalent to feof() or gzeof(). The end of file is reached if there
- * is no decompressed output in the overflow buffer and the end of the file
+ * LZ4 equivalent to feof() or gzeof().  Return true iff there is no
+ * decompressed output in the overflow buffer and the end of the backing file
  * is reached.
  */
 static int