savefile changes - part 1

This is the first of several savefile-related changes to
follow later. This one is groundwork for those later changes.

Remove internal compression schemes (RLECOMP and ZEROCOMP)
and discard the savefile_info struct that was primarily used to
convey which internal compression schemes had been in use.

Relocate some struct definitions into appropriate header files
for use by code to come in later changes.

Remove the two struct size-related fields from version_info and
from the nmakedefs_s. Instead, include a series of bytes near the
beginning of the savefile, representing the size of each
struct or base data type that impacts the historical savefile
content. Those are referred to as the "critical bytes".
(Related note: the "you" struct required two bytes, low and high,
due to its size).

Compare those critical bytes in a savefile against the NetHack
build that is reading the savefile. This allows mismatch detection
early in the savefile-reading process, and a clean exit, rather than
proceeding to read nonsensical values from the file. Include some
feedback on what the first mismatch was when encountering
one.

For arrays stored in the savefile, use loop-logic in the core
to write/read the array elements one at a time, rather than in
a single blob. This will be required for changes to follow later.
(impacts artiexist[], artidisco[], svd.dungeons[], svl.level_info[],
svl.level.locations[][], msrooms[] field of mapseen, svb.bases[],
svb.disco[] objects[], svm.mvitals[], svs.spl_book[], svd.doors[],
go.oracle_loc[], utrack[], wgrowtime[])

This also adds data model to the long version information.

This invalidates existing save and bones files due to the changes in
the information at the start of the file.

include/extern.h

@@ -67,6 +67,10 @@
  *
  */
 
+#ifndef ARTIFACT_H
+#include "artifact.h"
+#endif
+
 /* ### alloc.c ### */
 
 #if 0
@@ -3495,6 +3499,9 @@ extern unsigned long get_current_feature_ver(void);
 extern const char *copyright_banner_line(int) NONNULL;
 extern void early_version_info(boolean);
 extern void dump_version_info(void);
+extern void store_critical_bytes(NHFILE *) NONNULLARG1;
+extern int compare_critical_bytes(NHFILE *);
+extern int get_critical_size_count(void);
 
 /* ### video.c ### */