feat: overhaul userspace heap and virtual memory

programs/include/libc/montauk.h

@@ -190,6 +190,10 @@ extern "C" {
 #define MTK_SYS_WIFI_CONNECT_ASYNC 164
 #define MTK_SYS_NETIFS             165
 #define MTK_SYS_GETCHAR_NB         166
+#define MTK_SYS_UTIME              167
+#define MTK_SYS_MMAP_ANON          168
+#define MTK_SYS_MUNMAP             169
+#define MTK_SYS_MPROTECT           170
 /* @SYSCALLS-END */
 
 #define MTK_SOCK_TCP 1

programs/include/libc/sys/mman.h

@@ -10,10 +10,8 @@ extern "C" {
 #endif
 
 /*
-    * Anonymous-memory mmap over SYS_ALLOC. SYS_ALLOC returns
-    * page-aligned process memory, which is exactly what callers like
-    * GCC's page allocator need. File-backed mappings are not
-    * supported and fail with ENODEV.
+    * Demand-paged anonymous memory backed by the kernel's VMA subsystem.
+    * File-backed and shared mappings are not supported and fail cleanly.
 */
 
 #define PROT_NONE  0