Symbol names with more than two '.'s could be defined as constants

Dot-only names could also trip an assertion in `make develop`
when used as labels

test/asm/dots-constant.asm

@@ -0,0 +1,2 @@
+section "test", rom0
+def #... equs "sublocal"

test/asm/dots-constant.err

@@ -0,0 +1,3 @@
+error: syntax error, unexpected local label, expecting symbol
+    at dots-constant.asm(2)
+Assembly aborted with 1 error!

test/asm/dots-interpolate.asm

@@ -0,0 +1,2 @@
+section "test", rom0
+println "{...}"

test/asm/dots-interpolate.err

@@ -0,0 +1,2 @@
+FATAL: `...` is a nonsensical reference to a nested local label
+    at dots-interpolate.asm(2)

test/asm/dots-label.asm

@@ -0,0 +1,2 @@
+section "test", rom0
+#...:

test/asm/dots-label.err

@@ -0,0 +1,2 @@
+FATAL: `...` is a nonsensical reference to a nested local label
+    at dots-label.asm(2)

test/asm/dots-macro-arg.asm

@@ -0,0 +1,4 @@
+MACRO test
+	println "\<...>"
+ENDM
+	test 1, 2, 3, 4

test/asm/dots-macro-arg.err

@@ -0,0 +1,2 @@
+FATAL: `...` is a nonsensical reference to a nested local label
+    at dots-macro-arg.asm::test(2) <- dots-macro-arg.asm(4)

test/asm/label-scope.asm

@@ -16,3 +16,17 @@ ASSERT DEF(@) && DEF(.) && DEF(..) && DEF(Foo) && DEF(.bar)
 PRINTLN "PC: {#05X:@}"
 PRINTLN "global scope: \"{.}\" ({#05X:{.}})"
 PRINTLN "local scope: \"{..}\" ({#05X:{..}})"
+
+SECTION "can't redefine", ROM0
+
+#.
+#.:
+#.?
+DEF #. EQUS "global"
+jp #.
+
+#..
+#..:
+#..?
+DEF #.. EQUS "local"
+jp #..

test/asm/label-scope.err

@@ -10,4 +10,32 @@ error: Built-in symbol `.` cannot be purged
     at label-scope.asm(12)
 error: Built-in symbol `..` cannot be purged
     at label-scope.asm(12)
-Assembly aborted with 6 errors!
+error: `.` is not a macro
+    at label-scope.asm(22)
+error: `.` is not a macro
+    at label-scope.asm(23)
+error: `.` is not a macro
+    at label-scope.asm(24)
+error: `.` is reserved for a built-in symbol
+    at label-scope.asm(25)
+error: `.` has no value outside of a label scope
+    at label-scope.asm(26)
+warning: Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead [-Wobsolete]
+    at label-scope.asm(26)
+error: Strings as numbers must be a single charmap unit
+    at label-scope.asm(26)
+error: `..` is not a macro
+    at label-scope.asm(28)
+error: `..` is not a macro
+    at label-scope.asm(29)
+error: `..` is not a macro
+    at label-scope.asm(30)
+error: `..` is reserved for a built-in symbol
+    at label-scope.asm(31)
+error: `..` has no value outside of a local label scope
+    at label-scope.asm(32)
+warning: Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead [-Wobsolete]
+    at label-scope.asm(32)
+error: Strings as numbers must be a single charmap unit
+    at label-scope.asm(32)
+Assembly aborted with 18 errors!