Add recursion limit for INCLUDE and macros

(And REPT.)
Not exactly a *recursion* limit, more like a *stack depth* limit,
but calling it "recursion" conveys its purpose better.
The default of 64 is super overkill: even in a a project with
what I believe to be above-average levels of nesting, the
level only peaked at 6.
Keeping in mind the purpose of this is to catch infinite
recursion, which is still caught quickly (in usual cases, anyways),
this default seems sensible.
And it passes tests. What more do you need?

src/asm/main.c

@@ -315,6 +315,8 @@ int main(int argc, char *argv[])
 
 	/* yydebug=1; */
 
+	nMaxFileStackDepth = 64;
+
 	DefaultOptions.gbgfx[0] = '0';
 	DefaultOptions.gbgfx[1] = '1';
 	DefaultOptions.gbgfx[2] = '2';
@@ -332,7 +334,7 @@ int main(int argc, char *argv[])
 
 	newopt = CurrentOptions;
 
-	while ((ch = getopt(argc, argv, "b:D:Eg:hi:LM:o:p:Vvw")) != -1) {
+	while ((ch = getopt(argc, argv, "b:D:Eg:hi:LM:o:p:r:Vvw")) != -1) {
 		switch (ch) {
 		case 'b':
 			if (strlen(optarg) == 2) {
@@ -386,6 +388,12 @@ int main(int argc, char *argv[])
 				errx(1, "Argument for option 'p' must be between 0 and 0xFF");
 
 			break;
+		case 'r':
+			nMaxFileStackDepth = strtoul(optarg, &ep, 0);
+
+			if (optarg[0] == '\0' || *ep != '\0')
+				errx(1, "Invalid argument for option 'r'");
+			break;
 		case 'V':
 			printf("rgbasm %s\n", get_package_version_string());
 			exit(0);