Comment cleanup in sqliteInt.h.

FossilOrigin-Name: 67c3aea563e019083f0ed87b57982a0379637d4f
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 060b0d7..dd1d7c5 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -76,6 +76,11 @@
 #include <inttypes.h>
 #endif
 
+/*
+** The number of samples of an index that SQLite takes in order to 
+** construct a histogram of the table content when running ANALYZE
+** and with SQLITE_ENABLE_STAT2
+*/
 #define SQLITE_INDEX_SAMPLES 10
 
 /*
@@ -140,23 +145,18 @@
 **
 **     SQLITE_SYSTEM_MALLOC          // Use normal system malloc()
 **     SQLITE_MEMDEBUG               // Debugging version of system malloc()
-**     SQLITE_MEMORY_SIZE            // internal allocator #1
-**     SQLITE_MMAP_HEAP_SIZE         // internal mmap() allocator
-**     SQLITE_POW2_MEMORY_SIZE       // internal power-of-two allocator
+**
+** (Historical note:  There used to be several other options, but we've
+** pared it down to just these two.)
 **
 ** If none of the above are defined, then set SQLITE_SYSTEM_MALLOC as
 ** the default.
 */
-#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)+\
-    defined(SQLITE_MEMORY_SIZE)+defined(SQLITE_MMAP_HEAP_SIZE)+\
-    defined(SQLITE_POW2_MEMORY_SIZE)>1
+#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)>1
 # error "At most one of the following compile-time configuration options\
- is allows: SQLITE_SYSTEM_MALLOC, SQLITE_MEMDEBUG, SQLITE_MEMORY_SIZE,\
- SQLITE_MMAP_HEAP_SIZE, SQLITE_POW2_MEMORY_SIZE"
+ is allows: SQLITE_SYSTEM_MALLOC, SQLITE_MEMDEBUG"
 #endif
-#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)+\
-    defined(SQLITE_MEMORY_SIZE)+defined(SQLITE_MMAP_HEAP_SIZE)+\
-    defined(SQLITE_POW2_MEMORY_SIZE)==0
+#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)==0
 # define SQLITE_SYSTEM_MALLOC 1
 #endif
 
@@ -329,20 +329,6 @@
 #endif
 
 /*
-** If the following macro is set to 1, then NULL values are considered
-** distinct when determining whether or not two entries are the same
-** in a UNIQUE index.  This is the way PostgreSQL, Oracle, DB2, MySQL,
-** OCELOT, and Firebird all work.  The SQL92 spec explicitly says this
-** is the way things are suppose to work.
-**
-** If the following macro is set to 0, the NULLs are indistinct for
-** a UNIQUE index.  In this mode, you can only have a single NULL entry
-** for a column declared UNIQUE.  This is the way Informix and SQL Server
-** work.
-*/
-#define NULL_DISTINCT_FOR_UNIQUE 1
-
-/*
 ** The "file format" number is an integer that is incremented whenever
 ** the VDBE-level file format changes.  The following macros define the
 ** the default file format for new databases and the maximum file format
@@ -353,6 +339,10 @@
 # define SQLITE_DEFAULT_FILE_FORMAT 1
 #endif
 
+/*
+** Determine whether triggers are recursive by default.  This can be
+** changed at run-time using a pragma.
+*/
 #ifndef SQLITE_DEFAULT_RECURSIVE_TRIGGERS
 # define SQLITE_DEFAULT_RECURSIVE_TRIGGERS 0
 #endif
@@ -597,7 +587,6 @@
 typedef struct AuthContext AuthContext;
 typedef struct AutoincInfo AutoincInfo;
 typedef struct Bitvec Bitvec;
-typedef struct RowSet RowSet;
 typedef struct CollSeq CollSeq;
 typedef struct Column Column;
 typedef struct Db Db;
@@ -618,6 +607,7 @@
 typedef struct Module Module;
 typedef struct NameContext NameContext;
 typedef struct Parse Parse;
+typedef struct RowSet RowSet;
 typedef struct Savepoint Savepoint;
 typedef struct Select Select;
 typedef struct SrcList SrcList;
@@ -625,9 +615,9 @@
 typedef struct Table Table;
 typedef struct TableLock TableLock;
 typedef struct Token Token;
+typedef struct Trigger Trigger;
 typedef struct TriggerPrg TriggerPrg;
 typedef struct TriggerStep TriggerStep;
-typedef struct Trigger Trigger;
 typedef struct UnpackedRecord UnpackedRecord;
 typedef struct VTable VTable;
 typedef struct Walker Walker;
@@ -693,7 +683,7 @@
 
 /*
 ** These macros can be used to test, set, or clear bits in the 
-** Db.flags field.
+** Db.pSchema->flags field.
 */
 #define DbHasProperty(D,I,P)     (((D)->aDb[I].pSchema->flags&(P))==(P))
 #define DbHasAnyProperty(D,I,P)  (((D)->aDb[I].pSchema->flags&(P))!=0)
@@ -701,7 +691,7 @@
 #define DbClearProperty(D,I,P)   (D)->aDb[I].pSchema->flags&=~(P)
 
 /*
-** Allowed values for the DB.flags field.
+** Allowed values for the DB.pSchema->flags field.
 **
 ** The DB_SchemaLoaded flag is set after the database schema has been
 ** read into internal hash tables.
@@ -765,7 +755,7 @@
 };
 
 /*
-** Each database is an instance of the following structure.
+** Each database connection is an instance of the following structure.
 **
 ** The sqlite.lastRowid records the last insert rowid generated by an
 ** insert statement.  Inserts on views do not affect its value.  Each