Add dummy kbhit(), remove redundant documentation for cgetc().

doc/osi.sgml

@@ -139,8 +139,8 @@ There are no loadable drivers available.
 
 <sect1>conio implementation<p>
 
-The conio implementation is complete except for the kbhit() function. A
+The conio implementation is complete except for a working kbhit() function. 
-call to cgetc() always blocks until a character is entered.
+kbhit() currently returns true unconditionally.
 
 <sect1>stdio implementation<p>
 

libsrc/osic1p/kbhit.s

@@ -0,0 +1,11 @@
+;
+; int kbhit (void);
+;
+; Currently a dummy function that returns always true
+
+        .export         _kbhit
+
+_kbhit:
+        lda     #$01            ; load low byte with true value
+        ldx     #$00            ; load high byte
+        rts