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/mem2.c

@@ -344,6 +344,7 @@ static void *sqlite3MemRealloc(void *pPrior, int nByte){
   struct MemBlockHdr *pOldHdr;
   void *pNew;
   assert( mem.disallow==0 );
+  assert( (nByte & 7)==0 );     /* EV: R-46199-30249 */
   pOldHdr = sqlite3MemsysGetHeader(pPrior);
   pNew = sqlite3MemMalloc(nByte);
   if( pNew ){