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/global.h

@@ -357,8 +357,6 @@ struct version_info {
     unsigned long incarnation;   /* actual version number */
     unsigned long feature_set;   /* bitmask of config settings */
     unsigned long entity_count;  /* # of monsters and objects */
-    unsigned long struct_sizes1; /* size of key structs */
-    unsigned long struct_sizes2; /* size of more key structs */
 };
 
 struct savefile_info {
@@ -391,8 +389,6 @@ struct nomakedefs_s {
     unsigned long version_features;
     unsigned long ignored_features;
     unsigned long version_sanity1;
-    unsigned long version_sanity2;
-    unsigned long version_sanity3;
     unsigned long build_time;
 };
 extern struct nomakedefs_s nomakedefs;