iscntrl was not mentioned in the Makefile and therefor not built.

Change the isxxx functions to correctly handle values outside of character
range.


git-svn-id: svn://svn.cc65.org/cc65/trunk@33 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/common/isalpha.s

@@ -8,8 +8,14 @@
 	.import		__ctype
 
 _isalpha:
+	cpx	#$00		; Char range ok?
+	bne	@L1		; Jump if no
 	tay
 	lda	__ctype,y	; Get character classification
 	and 	#$03		; Mask character bits
 	rts
 
+@L1:	lda	#$00		; Return false
+	tax
+	rts
+