vec -> ivec

I'm going to implement a normal stable vector instead of an inline
vector so we have both options for use.  I think that's smarter than
just sticking to one.

ivec.c

@@ -0,0 +1,76 @@
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the Unlicense for details.
+
+ * You may distribute and modify this code under the terms of the Unlicense,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://unlicense.org/>.
+
+ * Created: 2025-08-19
+ * Description: Inline Vector implementation
+ */
+
+#include <malloc.h>
+#include <string.h>
+
+#include "./alisp.h"
+
+void ivec_make(void **ptr, u64 size)
+{
+  if (!ptr)
+    return;
+  ivec_t *ivector   = calloc(1, sizeof(*ivector) + size);
+  ivector->size     = 0;
+  ivector->capacity = size;
+  *ptr              = (ivector + 1);
+}
+
+void ivec_free(void **data)
+{
+  if (!data || !*data)
+    return;
+  free(IVEC_GET(*data));
+  *data = NULL;
+}
+
+void ivec_ensure_remaining(void **ptr, u64 space)
+{
+  if (!ptr || !*ptr)
+    return;
+  ivec_t *ivec = IVEC_GET(*ptr);
+  if (ivec->capacity - ivec->size < space)
+  {
+    void *new_ivec = NULL;
+    ivec_make(&new_ivec, MAX(ivec->capacity * IVEC_MULT, ivec->size + space));
+    IVEC_SIZE(new_ivec) = ivec->size;
+    memcpy(new_ivec, *ptr, ivec->size);
+    ivec_free(ptr);
+    *ptr = new_ivec;
+  }
+}
+
+void ivec_append_byte(void **ptr, u8 byte)
+{
+  ivec_ensure_remaining(ptr, 1);
+  ivec_t *ivec              = IVEC_GET(*ptr);
+  ivec->bytes[ivec->size++] = byte;
+}
+
+void ivec_append(void **ptr, void *data, u64 size)
+{
+  ivec_ensure_remaining(ptr, size);
+  ivec_t *ivec = IVEC_GET(*ptr);
+  memcpy(*ptr + ivec->size, data, size);
+  ivec->size += size;
+}
+
+void ivec_clone(void **dest, void **src)
+{
+  if (!dest || !src || !*src)
+    return;
+  ivec_make(dest, IVEC_SIZE(*src));
+  memcpy(*dest, *src, IVEC_SIZE(*src));
+  IVEC_SIZE(*dest) = IVEC_SIZE(*src);
+}