Add errstr manual page

doc/apps/errstr.pod

@@ -0,0 +1,39 @@
+=pod
+
+=head1 NAME
+
+errstr - lookup error codes
+
+=head1 SYNOPSIS
+
+B<openssl errstr error_code>
+
+=head1 DESCRIPTION
+
+Sometimes an application will not load error message and only
+numerical forms will be available. The B<errstr> utility can be used to 
+display the meaning of the hex code. The hex code is the hex digits after the
+second colon.
+
+=head1 EXAMPLE
+
+The error code:
+
+ 27594:error:2006D080:lib(32):func(109):reason(128):bss_file.c:107:
+
+can be displayed with:
+ 
+ openssl errstr 2006D080
+
+to produce the error message:
+
+ error:2006D080:BIO routines:BIO_new_file:no such file
+
+=head1 SEE ALSO
+
+L<err(3)|err(3)>,
+L<ERR_load_crypto_strings(3)|ERR_load_crypto_strings(3)>,
+L<SSL_load_error_strings(3)|SSL_load_error_strings(3)>
+
+
+=cut