Add evidence mark comments to source code. Add additional information to the

documentation of sqlite3_release_memory().  Fix a minor inefficiency in mem1.c
that was discovered while writing requirements tests.

FossilOrigin-Name: 53b0c03fd33d2d8141fd386de5493fec64456042

src/util.c

@@ -215,6 +215,12 @@ int sqlite3Dequote(char *z){
 /*
 ** Some systems have stricmp().  Others have strcasecmp().  Because
 ** there is no consistency, we will define our own.
+**
+** IMPLEMENTATION-OF: R-20522-24639 The sqlite3_strnicmp() API allows
+** applications and extensions to compare the contents of two buffers
+** containing UTF-8 strings in a case-independent fashion, using the same
+** definition of case independence that SQLite uses internally when
+** comparing identifiers.
 */
 int sqlite3StrICmp(const char *zLeft, const char *zRight){
   register unsigned char *a, *b;