Apple2: Provide a way to get directory file count

The information is available in the directory key block.
Providing it to the user as soon as opendir() is done
can save them costly code.

doc/apple2.sgml

@@ -332,6 +332,7 @@ usage.
 <item>_datetime
 <item>allow_lowercase
 <item>beep
+<item>dir_file_count
 <item>get_ostype
 <item>gmtime_dt
 <item>mktime_dt

doc/apple2enh.sgml

@@ -332,6 +332,7 @@ usage.
 <item>_filetype
 <item>_datetime
 <item>beep
+<item>dir_file_count
 <item>get_ostype
 <item>gmtime_dt
 <item>mktime_dt

doc/funcref.sgml

@@ -97,6 +97,7 @@ function.
 <item>_dos_type
 <item>allow_lowercase
 <item><ref id="beep" name="beep">
+<item><ref id="dir_file_count" name="dir_file_count">
 <item><ref id="get_ostype" name="get_ostype">
 <item><ref id="gmtime_dt" name="gmtime_dt">
 <item><ref id="mktime_dt" name="mktime_dt">
@@ -109,6 +110,7 @@ function.
 <itemize>
 <item>_dos_type
 <item><ref id="beep" name="beep">
+<item><ref id="dir_file_count" name="dir_file_count">
 <item><ref id="get_ostype" name="get_ostype">
 <item><ref id="gmtime_dt" name="gmtime_dt">
 <item><ref id="mktime_dt" name="mktime_dt">
@@ -3524,6 +3526,25 @@ used in presence of a prototype.
 </quote>
 
 
+<sect1>dir_file_count<label id="dir_file_count"><p>
+
+<quote>
+<descrip>
+<tag/Function/Returns the number of files in the directory.
+<tag/Header/<tt/<ref id="apple2.h" name="apple2.h">/
+<tag/Declaration/<tt/unsigned int __fastcall__ dir_file_count(DIR *dir);/
+<tag/Description/<tt/dir_file_count/ is machine dependent and does not exist for
+all supported targets. If it exists, it returns the number of active
+(non-deleted) files in the directory.
+<tag/Notes/<itemize>
+<item>The function does not exist on all platforms.
+</itemize>
+<tag/Availability/cc65 (not all platforms)
+<tag/Example/None.
+</descrip>
+</quote>
+
+
 <sect1>div<label id="div"><p>
 
 <quote>