Small documentation fixes by shagol (closes #20).

doc/modbus_close.txt

@@ -9,7 +9,7 @@ modbus_close - close a Modbus connection
 
 SYNOPSIS
 --------
-*int modbus_close(modbus_t *'ctx');*
+*void modbus_close(modbus_t *'ctx');*
 
 
 DESCRIPTION
@@ -20,8 +20,7 @@ backend set in the context.
 
 RETURN VALUE
 ------------
-The _modbus_close()_ function shall return 0 if successful. Otherwise it shall
-return -1 and set errno.
+There is no return value.
 
 
 EXAMPLE

doc/modbus_get_header_length.txt

@@ -15,7 +15,7 @@ SYNOPSIS
 DESCRIPTION
 -----------
 The _modbus_get_header_length()_ function shall retrieve the current header
-length from the backend. This fonction is convenient to manipulate a message and
+length from the backend. This function is convenient to manipulate a message and
 so its limited to low-level operations.
 
 

doc/modbus_read_input_bits.txt

@@ -21,7 +21,7 @@ in 'dest' array as unsigned bytes (8 bits) set to _TRUE_ or _FALSE_.
 You must take care to allocate enough memory to store the results in 'dest'
 (at least 'nb' * sizeof(uint8_t)).
 
-The function uses the Modbus function code 0x03 (read input status).
+The function uses the Modbus function code 0x02 (read input status).
 
 
 RETURN VALUE