Significantly overhaul OPT code

Simplify the mess that was option setting (2 redundant variables !?)
Move options to a separate file
Have "modules" own their options, and OPT only access them (less redundancy)
Simplify code, respect naming conventions better

src/asm/opt.c

@@ -0,0 +1,111 @@
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "asm/lexer.h"
+#include "asm/section.h"
+#include "asm/warning.h"
+
+struct OptStackEntry {
+	char binary[2];
+	char gbgfx[4];
+	int32_t fillByte;
+	struct OptStackEntry *next;
+};
+
+static struct OptStackEntry *stack = NULL;
+
+void opt_B(char chars[2])
+{
+	lexer_SetBinDigits(chars);
+}
+
+void opt_G(char chars[4])
+{
+	lexer_SetGfxDigits(chars);
+}
+
+void opt_P(uint8_t fill)
+{
+	fillByte = fill;
+}
+
+void opt_Parse(char *s)
+{
+	switch (s[0]) {
+	case 'b':
+		if (strlen(&s[1]) == 2)
+			opt_B(&s[1]);
+		else
+			error("Must specify exactly 2 characters for option 'b'\n");
+		break;
+
+	case 'g':
+		if (strlen(&s[1]) == 4)
+			opt_G(&s[1]);
+		else
+			error("Must specify exactly 4 characters for option 'g'\n");
+		break;
+
+	case 'p':
+		if (strlen(&s[1]) <= 2) {
+			int result;
+			unsigned int fillchar;
+
+			result = sscanf(&s[1], "%x", &fillchar);
+			if (result != EOF && result != 1)
+				error("Invalid argument for option 'p'\n");
+			else
+				opt_P(fillchar);
+		} else {
+			error("Invalid argument for option 'p'\n");
+		}
+		break;
+
+	default:
+		error("Unknown option '%c'\n", s[0]);
+		break;
+	}
+}
+
+void opt_Push(void)
+{
+	struct OptStackEntry *entry = malloc(sizeof(*entry));
+
+	if (entry == NULL)
+		fatalerror("Failed to alloc option stack entry: %s\n", strerror(errno));
+
+	// Both of these pulled from lexer.h
+	entry->binary[0] = binDigits[0];
+	entry->binary[1] = binDigits[1];
+
+	entry->gbgfx[0] = gfxDigits[0];
+	entry->gbgfx[1] = gfxDigits[1];
+	entry->gbgfx[2] = gfxDigits[2];
+	entry->gbgfx[3] = gfxDigits[3];
+
+	entry->fillByte = fillByte; // Pulled from section.h
+
+	entry->next = stack;
+	stack = entry;
+}
+
+void opt_Pop(void)
+{
+	if (stack == NULL) {
+		error("No entries in the option stack\n");
+		return;
+	}
+
+	struct OptStackEntry *entry = stack;
+
+	opt_B(entry->binary);
+	opt_G(entry->gbgfx);
+	opt_P(entry->fillByte);
+	stack = entry->next;
+	free(entry);
+}