Fix bugs with new memory manager

This fixes a regression in mmap(MAP_FIXED) on Windows caused by a recent
revision. This change also fixes ZipOS so it no longer needs a MAP_FIXED
mapping to open files from the PKZIP store. The memory mapping mutex was
implemented incorrectly earlier which meant that ftrace and strace could
cause cause crashes. This lock and other recursive mutexes are rewritten
so that it should be provable that recursive mutexes in cosmopolitan are
asynchronous signal safe.

libc/calls/struct/sigset.internal.h

@@ -2,17 +2,30 @@
 #define COSMOPOLITAN_LIBC_CALLS_STRUCT_SIGSET_INTERNAL_H_
 #include "libc/calls/struct/sigset.h"
 #include "libc/mem/alloca.h"
+#include "libc/sysv/consts/sig.h"
 COSMOPOLITAN_C_START_
 
+#ifndef MODE_DBG
+/* block sigs because theoretical edge cases */
 #define BLOCK_SIGNALS  \
   do {                 \
     sigset_t _SigMask; \
   _SigMask = __sig_block()
-
 #define ALLOW_SIGNALS      \
   __sig_unblock(_SigMask); \
   }                        \
   while (0)
+#else
+/* doesn't block signals so we can get a crash
+   report, when a core runtime library crashes */
+#define BLOCK_SIGNALS  \
+  do {                 \
+    sigset_t _SigMask; \
+  sigprocmask(SIG_SETMASK, 0, &_SigMask)
+#define ALLOW_SIGNALS \
+  }                   \
+  while (0)
+#endif
 
 sigset_t __sig_block(void);
 void __sig_unblock(sigset_t);