Support C-Style enum in preproc (#1984)

* [preproc] C-style enums

- asm files parseable from stdin
- 2nd preproc pass
- add parser for C-style `enum`
- positional arguments at end of command

---------

Co-authored-by: sbird <sbird@no.tld>
Co-authored-by: Martin Griffin <martinrgriffin@gmail.com>

tools/preproc/io.cpp

@@ -0,0 +1,51 @@
+#include "preproc.h"
+#include "io.h"
+#include <string>
+#include <cerrno>
+#include <cstring>
+
+char *ReadFileToBuffer(const char *filename, bool isStdin, long *size)
+{
+    FILE *fp;
+    if (isStdin)
+        fp = stdin;
+    else
+        fp = std::fopen(filename, "rb");
+
+    if (fp == NULL)
+        FATAL_ERROR("Failed to open \"%s\" for reading.\n", filename);
+
+    *size = 0;
+    char *buffer = (char *)malloc(CHUNK_SIZE + 1);
+    if (buffer == NULL) {
+        FATAL_ERROR("Failed to allocate memory to process file \"%s\"!", filename);
+    }
+
+    std::size_t numAllocatedBytes = CHUNK_SIZE + 1;
+    std::size_t bufferOffset = 0;
+    std::size_t count;
+
+    while ((count = std::fread(buffer + bufferOffset, 1, CHUNK_SIZE, fp)) != 0) {
+        if (!std::ferror(fp)) {
+            *size += count;
+
+            if (std::feof(fp)) {
+                break;
+            }
+
+            numAllocatedBytes += CHUNK_SIZE;
+            bufferOffset += CHUNK_SIZE;
+            buffer = (char *)realloc(buffer, numAllocatedBytes);
+            if (buffer == NULL) {
+                FATAL_ERROR("Failed to allocate memory to process file \"%s\"!", filename);
+            }
+        } else {
+            FATAL_ERROR("Failed to read \"%s\". (error: %s)", filename, std::strerror(errno));
+        }
+    }
+
+    buffer[*size] = 0;
+
+    std::fclose(fp);
+    return buffer;
+}