Slightly better handling of low HBIOS heap memory

CBIOS reports *** HBIOS Heap Overflow, when the HBIOS is big (i.e. lots of included drivers)

Trigger build failure when CCP will not fit in heap.
Slightly more informative CBIOS error message

Source/CBIOS/cbios.asm

@@ -2381,7 +2381,7 @@ INIT3:
 ;
 ERR_BIOMEM:
 	CALL	NEWLINE2		; FORMATTING
-	LD	DE,STR_BIOMEM		; HBIOS HEAP MEM OVERFLOW
+	LD	DE,STR_HEAPOVF		; HBIOS HEAP MEM OVERFLOW
 	CALL	WRITESTR		; TELL THE USER
 	CALL	PANIC			; AND GRIND TO A SCREACHING HALT
 ;
@@ -3436,7 +3436,7 @@ STR_INITRAMDISK	.DB	"Formatting RAMDISK...$"
 STR_LDR2	.DB	"\r\n"
 STR_LDR		.DB	"\r\n	$"
 STR_DPHINIT	.DB	"Configuring Drives...$"
-STR_HEAPOVF	.DB	" *** Insufficient Memory ***$"
+STR_HEAPOVF	.DB	" *** Insufficient HBIOS Heap Memory ***$"
 STR_INVMED	.DB	" *** Invalid Device ID ***$"
 STR_VERMIS	.DB	7,"*** WARNING: HBIOS/CBIOS Version Mismatch ***$"
 STR_MEMFREE	.DB	" Disk Buffer Bytes Free$"
@@ -3444,7 +3444,6 @@ STR_CPM		.DB	"CP/M-80 v2.2$"
 STR_ZSDOS	.DB	"ZSDOS v1.1$"
 STR_TPA1	.DB	", $"
 STR_TPA2	.DB	"K TPA$"
-STR_BIOMEM	.DB	"*** HBIOS Heap Overflow ***$"
 
 #IFDEF PLTUNA
 INIBUF	.FILL	512,0			; LOCATION OF TEMP WORK BUF DURING INIT (512 BYTES)

Source/HBIOS/hbios.asm

@@ -7305,6 +7305,16 @@ SLACK		.EQU	BNKTOP - $
 		.ECHO	"HBIOS space remaining: "
 		.ECHO	SLACK
 		.ECHO	" bytes.\n"
+
+#IF (SLACK<0)
+		.ECHO	"*** ERROR: HBIOS too big.\n"
+		!!!	; FORCE AN ASSEMBLY ERROR
+#ENDIF
+;
+#IF (CCP_SIZ > SLACK)
+		.ECHO	"*** ERROR: Insufficient space for CBIOS Cache.\n"
+		!!!	; FORCE AN ASSEMBLY ERROR
+#ENDIF
 ;
 #IFDEF ROMBOOT
   #IF (ROMSIZE > 0)