Switch to the more complete Snes9x 1.53 documentation.

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+***** Important notice ********************************************************
+  This document describes the snapshot file format for Snes9x 1.52 and later,
+  not compatible with 1.51.
+*******************************************************************************
+
+  Snes9x snapshot file format: (may be gzip-compressed)
+
+  Begins with fixed length signature, consisting of a string, ':', a 4-digit
+  decimal version, and a '\n'.
+
+#!s9xsnp:0006   <-- '\n' after the 6
+
+  Then we have various blocks. The block format is: 3-character block name,
+  ':', 6-digit length, ':', then the data. Blocks are written in a defined
+  order. Structs are written packed with their members in a defined order, in
+  big-endian order where applicable.
+
+NAM:000019:Chrono Trigger.zip
+
+  Currently defined blocks (in order) are:
+
+    Essential parts:
+      NAM - ROM filename, from Memory.ROMFilename. 0-terminated string.
+      CPU - struct SCPUState, CPU internal state variables.
+      REG - struct SRegisters, emulated CPU registers.
+      PPU - struct SPPU, PPU internal variables. Note that IPPU is never saved.
+      DMA - struct SDMA, DMA/HDMA state variables.
+      VRA - Memory.VRAM, 0x10000 bytes.
+      RAM - Memory.RAM, 0x20000 bytes (WRAM).
+      SRA - Memory.SRAM, 0x20000 bytes.
+      FIL - Memory.FillRAM, 0x8000 bytes (register backing store).
+      SND - All of sound emulated registers and state valiables.
+      CTL - struct SControlSnapshot, controller emulation.
+      TIM - struct STimings, variables about timings between emulated events.
+
+    Optional parts:
+      SFX - struct FxRegs_s, Super FX.
+      SA1 - struct SSA1, SA1 internal state variables.
+      SAR - struct SSA1Registers, SA1 emulated registers.
+      DP1 - struct SDSP1, DSP-1.
+      DP2 - struct SDSP2, DSP-2.
+      DP4 - struct SDSP4, DSP-4.
+      CX4 - Memory.C4RAM, 0x2000 bytes.
+      ST0 - struct SST010, ST-010.
+      OBC - struct SOBC1, OBC1 internal state variables.
+      OBM - Memory.OBC1RAM, 0x2000 byts.
+      S71 - struct SSPC7110Snapshot, SPC7110.
+      SRT - struct SSRTCSnapshot, S-RTC internal state variables.
+      CLK - struct SRTCData, S-RTC emulated registers.
+      BSX - struct SBSX, BS-X.
+      SHO - rendered SNES screen.
+      MOV - struct SnapshotMovieInfo.
+      MID - Some block of data the movie subsystem.
+
+==================
+
+Without changing the snapshot version number:
+---------------------------------------------
+
+Blocks may be safely added at the END of the file, as anything after the last
+block is ignored. Blocks may not be moved or removed.
+
+Blocks may not decrease in size. Say you decrease from 10 bytes to 5. Then
+later you increase back to 8. The only way you could safely do this is if
+bytes 5-7 still mean the same thing they meant when the block was 10 bytes
+long.
+
+Blocks may increase in size as you wish, as long as you can handle old
+savestates with the old shorter size.
+
+Struct members may not change in interpretation. New struct members may be
+added (at the END!) only if you can cope with them being binary-0 in older
+savestates. Struct members may not be removed or changed in size/type.
+
+With changing the snapshot version number:
+------------------------------------------
+
+Blocks may be added, moved, or removed at will.
+
+Blocks may decrease in size.
+
+Struct members may be added, moved, or deleted, and their
+interpretations/types may be changed. Use the 'debuted_in' and 'deleted_in'
+fields to indicate when the new member debuted or the old member went away.