Fixes and improvements to KIM-1 i/o routines.

Tested on real KIM-1 hardware.

read.s:
- Remove commented out line.
- Remove unused check for bell character.
- Remove echo of newline (hardware always echoes entered characters).
- This fixes gets() and fgets() so they return when CR is entered.

write.s:
- Fix check for adding return after linefeed (failed to work because OUTCHR changes A)
- Remove unused check for bell character.

kim1.inc:
- Add symbol for monitor entry

crt0.s:
- Jump to KIM-1 monitor by address rather than using BRK (which relies on vector being set in RAM)

libsrc/kim1/read.s

@@ -27,15 +27,10 @@ begin:  dec     ptr2
         beq     done             ; If buffer full, return
 
 getch:  jsr     INTCHR           ; Get character using Monitor ROM call
-        ;jsr     OUTCHR           ; Echo it
         and     #$7F             ; Clear top bit
-        cmp     #$07             ; Check for '\a'
-        bne     chkcr            ; ...if BEL character
-        ;jsr     BEEP             ; Make beep sound TODO
-chkcr:  cmp     #$0D             ; Check for '\r'
+        cmp     #$0D             ; Check for '\r'
         bne     putch            ; ...if CR character
         lda     #$0A             ; Replace with '\n'
-        jsr     OUTCHR           ; and echo it
 
 putch:  ldy     #$00             ; Put char into return buffer
         sta     (ptr1),y