Add modbus_[get|set]_indication_timeout to doc build

doc/Makefile.am

@@ -3,6 +3,8 @@ TXT3 = \
         modbus_connect.txt \
         modbus_flush.txt \
         modbus_free.txt \
+        modbus_get_indication_timeout.txt \
+        modbus_get_slave.txt \
         modbus_get_byte_from_bits.txt \
         modbus_get_byte_timeout.txt \
         modbus_get_float.txt \
@@ -12,7 +14,6 @@ TXT3 = \
         modbus_get_float_dcba.txt \
         modbus_get_header_length.txt \
         modbus_get_response_timeout.txt \
-	modbus_get_slave.txt \
         modbus_get_socket.txt \
         modbus_mapping_free.txt \
         modbus_mapping_new.txt \
@@ -48,6 +49,7 @@ TXT3 = \
         modbus_set_float_badc.txt \
         modbus_set_float_cdab.txt \
         modbus_set_float_dcba.txt \
+        modbus_set_indication_timeout.txt \
         modbus_set_response_timeout.txt \
         modbus_set_slave.txt \
         modbus_set_socket.txt \