Make the internal dynamic string interface available to extensions using
the new sqlite3_str object and its associated methods.  This is mostly just
a renaming of internal objects and methods to use external names, through
there are a few small wrapper functions.

FossilOrigin-Name: 87f261f0cb800b06ad786f6df16f2c4dddd0d93dfdcc77b4a4eaa22920b56bf1
diff --git a/src/treeview.c b/src/treeview.c
index 562743e..970d85e 100644
--- a/src/treeview.c
+++ b/src/treeview.c
@@ -58,16 +58,16 @@
   sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);
   if( p ){
     for(i=0; i<p->iLevel && i<sizeof(p->bLine)-1; i++){
-      sqlite3StrAccumAppend(&acc, p->bLine[i] ? "|   " : "    ", 4);
+      sqlite3_str_append(&acc, p->bLine[i] ? "|   " : "    ", 4);
     }
-    sqlite3StrAccumAppend(&acc, p->bLine[i] ? "|-- " : "'-- ", 4);
+    sqlite3_str_append(&acc, p->bLine[i] ? "|-- " : "'-- ", 4);
   }
   if( zFormat!=0 ){
     va_start(ap, zFormat);
-    sqlite3VXPrintf(&acc, zFormat, ap);
+    sqlite3_str_vappendf(&acc, zFormat, ap);
     va_end(ap);
     assert( acc.nChar>0 );
-    sqlite3StrAccumAppend(&acc, "\n", 1);
+    sqlite3_str_append(&acc, "\n", 1);
   }
   sqlite3StrAccumFinish(&acc);
   fprintf(stdout,"%s", zBuf);
@@ -101,17 +101,17 @@
       char zLine[1000];
       const struct Cte *pCte = &pWith->a[i];
       sqlite3StrAccumInit(&x, 0, zLine, sizeof(zLine), 0);
-      sqlite3XPrintf(&x, "%s", pCte->zName);
+      sqlite3_str_appendf(&x, "%s", pCte->zName);
       if( pCte->pCols && pCte->pCols->nExpr>0 ){
         char cSep = '(';
         int j;
         for(j=0; j<pCte->pCols->nExpr; j++){
-          sqlite3XPrintf(&x, "%c%s", cSep, pCte->pCols->a[j].zName);
+          sqlite3_str_appendf(&x, "%c%s", cSep, pCte->pCols->a[j].zName);
           cSep = ',';
         }
-        sqlite3XPrintf(&x, ")");
+        sqlite3_str_appendf(&x, ")");
       }
-      sqlite3XPrintf(&x, " AS");
+      sqlite3_str_appendf(&x, " AS");
       sqlite3StrAccumFinish(&x);
       sqlite3TreeViewItem(pView, zLine, i<pWith->nCte-1);
       sqlite3TreeViewSelect(pView, pCte->pSelect, 0);
@@ -176,20 +176,20 @@
         StrAccum x;
         char zLine[100];
         sqlite3StrAccumInit(&x, 0, zLine, sizeof(zLine), 0);
-        sqlite3XPrintf(&x, "{%d,*}", pItem->iCursor);
+        sqlite3_str_appendf(&x, "{%d,*}", pItem->iCursor);
         if( pItem->zDatabase ){
-          sqlite3XPrintf(&x, " %s.%s", pItem->zDatabase, pItem->zName);
+          sqlite3_str_appendf(&x, " %s.%s", pItem->zDatabase, pItem->zName);
         }else if( pItem->zName ){
-          sqlite3XPrintf(&x, " %s", pItem->zName);
+          sqlite3_str_appendf(&x, " %s", pItem->zName);
         }
         if( pItem->pTab ){
-          sqlite3XPrintf(&x, " tabname=%Q", pItem->pTab->zName);
+          sqlite3_str_appendf(&x, " tabname=%Q", pItem->pTab->zName);
         }
         if( pItem->zAlias ){
-          sqlite3XPrintf(&x, " (AS %s)", pItem->zAlias);
+          sqlite3_str_appendf(&x, " (AS %s)", pItem->zAlias);
         }
         if( pItem->fg.jointype & JT_LEFT ){
-          sqlite3XPrintf(&x, " LEFT-JOIN");
+          sqlite3_str_appendf(&x, " LEFT-JOIN");
         }
         sqlite3StrAccumFinish(&x);
         sqlite3TreeViewItem(pView, zLine, i<p->pSrc->nSrc-1);