Add a -Wunmapped-char warning for characters not in the charmap (#1023)

Fixes #1022

test/asm/charlen-charsub.asm

@@ -1,3 +1,4 @@
+	opt Wno-unmapped-char
 	charmap "<NULL>", $00
 	charmap "A", $10
 	charmap "B", $20

test/asm/multiple-charmaps.asm

@@ -1,3 +1,5 @@
+opt Wno-unmapped-char
+
 new_: MACRO
 	IF _NARG > 1
 	println "newcharmap \1, \2"

test/asm/multiple-charmaps.err

@@ -1,19 +1,19 @@
-warning: multiple-charmaps.asm(39) -> multiple-charmaps.asm::print_mapped(27): [-Wnumeric-string]
+warning: multiple-charmaps.asm(41) -> multiple-charmaps.asm::print_mapped(29): [-Wnumeric-string]
     Treating 2-character string as a number
-warning: multiple-charmaps.asm(47) -> multiple-charmaps.asm::print_mapped(27): [-Wnumeric-string]
+warning: multiple-charmaps.asm(49) -> multiple-charmaps.asm::print_mapped(29): [-Wnumeric-string]
     Treating 2-character string as a number
-warning: multiple-charmaps.asm(66) -> multiple-charmaps.asm::print_mapped(27): [-Wnumeric-string]
+warning: multiple-charmaps.asm(68) -> multiple-charmaps.asm::print_mapped(29): [-Wnumeric-string]
     Treating 2-character string as a number
-warning: multiple-charmaps.asm(89) -> multiple-charmaps.asm::print_mapped(27): [-Wnumeric-string]
+warning: multiple-charmaps.asm(91) -> multiple-charmaps.asm::print_mapped(29): [-Wnumeric-string]
     Treating 2-character string as a number
-warning: multiple-charmaps.asm(90) -> multiple-charmaps.asm::print_mapped(27): [-Wnumeric-string]
+warning: multiple-charmaps.asm(92) -> multiple-charmaps.asm::print_mapped(29): [-Wnumeric-string]
     Treating 2-character string as a number
-warning: multiple-charmaps.asm(98) -> multiple-charmaps.asm::print_mapped(27): [-Wnumeric-string]
+warning: multiple-charmaps.asm(100) -> multiple-charmaps.asm::print_mapped(29): [-Wnumeric-string]
     Treating 2-character string as a number
-error: multiple-charmaps.asm(100) -> multiple-charmaps.asm::new_(7):
+error: multiple-charmaps.asm(102) -> multiple-charmaps.asm::new_(9):
     Charmap 'map1' already exists
-error: multiple-charmaps.asm(102) -> multiple-charmaps.asm::set_(13):
+error: multiple-charmaps.asm(104) -> multiple-charmaps.asm::set_(15):
     Charmap 'map5' doesn't exist
-error: multiple-charmaps.asm(104) -> multiple-charmaps.asm::pop_(23):
+error: multiple-charmaps.asm(106) -> multiple-charmaps.asm::pop_(25):
     No entries in the charmap stack
 error: Assembly aborted (3 errors)!

test/asm/unmapped-char.asm

@@ -0,0 +1,18 @@
+SECTION "test", ROM0
+
+	db "A" ; OK, default empty charmap
+
+	pushc
+	newcharmap custom
+	db "A" ; unmapped in non-default charmap
+	popc
+
+	db "A" ; OK, default empty charmap again
+
+	charmap "B", $42
+	db "A" ; unmapped in non-empty charmap
+
+	println "A" ; does not use charmap
+
+	opt Wno-unmapped-char
+	db "A" ; warning silenced

test/asm/unmapped-char.err

@@ -0,0 +1,4 @@
+warning: unmapped-char.asm(7): [-Wunmapped-char]
+    Unmapped character 'A'
+warning: unmapped-char.asm(13): [-Wunmapped-char]
+    Unmapped character 'A'

test/asm/unmapped-char.out

@@ -0,0 +1 @@
+A

test/asm/unmapped-char.out.bin

@@ -0,0 +1 @@
+AAAAA

test/asm/warn-numeric-string.asm

@@ -1,6 +1,6 @@
+opt Wno-unmapped-char
 charmap "<NULL>", $00
 
-
 SECTION "ROM", ROM0
 
 MACRO try