Fixed a few doco strings.

src/devices/sound/ay8910.cpp

@@ -149,7 +149,7 @@
   The rewrite also introduces a generic model for the DAC. This model is
   not perfect, but allows channel mixing based on a parametrized approach.
   This model also allows to factor in different loads on individual channels.
-  If a better model is developped in the future or better measurements are
+  If a better model is developed in the future or better measurements are
   available, the driver should be easy to change. The model is described
   later.
 

src/mame/drivers/hk68v10.cpp

@@ -378,6 +378,7 @@ ROM_START (hk68v10)
 	 *  'bw'       Boot from Winchester
 	 *  'bf'       Boot from floppy (MIO, SBX-FDIO)
 	 *  'bsf'      Boot from floppy (SCSI)
+	 *  'x'        Display registers
 	 *
 	 * Setup sequence channel B
 	 * :scc B Reg 04 <- 4c x16 clock, 2 stop bits, no parity

src/mame/drivers/itt3030.cpp

@@ -4,6 +4,8 @@
 
     ITT 3030
 
+    When the machine is started you get a black screen.
+    Hold down B until the cursor appears. It will then boot from the floppy.
 
     ToDo:
     - Check Beeper

src/mame/drivers/thomson.cpp

@@ -115,7 +115,7 @@
 /* ------------- game port ------------- */
 
 /*
-  Two generations of game port extensions were developped
+  Two generations of game port extensions were developed
 
   - CM 90-112 (model 1)
     connect up to two 8-position 1-button game pads