Use code points instead of bytes for STRSUB/STRLEN

test/asm/strlen.asm

@@ -0,0 +1,9 @@
+SECTION "sec", ROM0
+
+xstrlen: MACRO
+	PRINTV STRLEN(\1)
+	PRINTT "\n"
+ENDM
+
+	xstrlen "ABC"
+	xstrlen "カタカナ"

test/asm/strlen.out

@@ -0,0 +1,2 @@
+$3
+$4

test/asm/strsub.asm

@@ -0,0 +1,22 @@
+SECTION "sec", ROM0
+
+xstrsub: MACRO
+	PRINTT STRSUB(\1, \2, \3)
+	PRINTT "\n"
+ENDM
+
+	xstrsub "ABC", 1, 1
+	xstrsub "ABC", 2, 1
+	xstrsub "ABC", 3, 1
+	xstrsub "ABC", 1, 2
+	xstrsub "ABC", 2, 2
+	xstrsub "ABC", 2, 32
+	xstrsub "ABC", 2, 300
+	xstrsub "ABC", 0, 300
+	xstrsub "ABC", 4, 0
+	xstrsub "ABC", 4, 1
+	xstrsub "カタカナ", 1, 2
+	xstrsub "カタカナ", 3, 2
+	xstrsub "カタカナ", 3, 10
+	xstrsub "g̈", 1, 1
+	xstrsub "g̈", 1, 2

test/asm/strsub.out

@@ -0,0 +1,31 @@
+warning: strsub.asm(13) -> xstrsub(1):
+    STRSUB: Length too big: 32
+warning: strsub.asm(14) -> xstrsub(1):
+    STRSUB: Length too big: 300
+warning: strsub.asm(15) -> xstrsub(1):
+    STRSUB: Position starts at 1
+warning: strsub.asm(15) -> xstrsub(1):
+    STRSUB: Length too big: 300
+warning: strsub.asm(16) -> xstrsub(1):
+    STRSUB: Position 4 is past the end of the string
+warning: strsub.asm(17) -> xstrsub(1):
+    STRSUB: Position 4 is past the end of the string
+warning: strsub.asm(17) -> xstrsub(1):
+    STRSUB: Length too big: 1
+warning: strsub.asm(20) -> xstrsub(1):
+    STRSUB: Length too big: 10
+A
+B
+C
+AB
+BC
+BC
+BC
+ABC
+
+
+カタ
+カナ
+カナ
+g
+g̈