Tests connect.odbc_postgresql and connect.odbc_oracle failed

after revision 4363 (fixes for MDEV-6661 and MDEV-6666).

Fixing a wrong assumption in ha_connect.cc that strings
returned from val_str() are always 0-terminated.

storage/connect/ha_connect.cc

@@ -2188,8 +2188,7 @@ PFIL ha_connect::CondFilter(PGLOBAL g, Item *cond)
         switch (args[i]->real_type()) {
           case COND::STRING_ITEM:
             pp->Type= TYPE_STRING;
-            pp->Value= PlugSubAlloc(g, NULL, res->length() + 1);
-            strncpy((char*)pp->Value, res->ptr(), res->length() + 1);
+            pp->Value= PlugSubAllocStr(g, NULL, res->ptr(), res->length());
             break;
           case COND::INT_ITEM:
             pp->Type= TYPE_INT;
@@ -2437,7 +2436,7 @@ PCFIL ha_connect::CheckCond(PGLOBAL g, PCFIL filp, AMT tty, Item *cond)
         } else {
           if (args[i]->field_type() == MYSQL_TYPE_VARCHAR) {
             // Add the command to the list
-            PCMD *ncp, cmdp= new(g) CMD(g, (char*)res->ptr());
+            PCMD *ncp, cmdp= new(g) CMD(g, (char*)res->c_ptr());
 
             for (ncp= &filp->Cmds; *ncp; ncp= &(*ncp)->Next) ;
 

storage/connect/ha_connect.h

@@ -174,6 +174,16 @@ class ha_connect: public handler
   CONNECT_SHARE *share;        ///< Shared lock info
   CONNECT_SHARE *get_share();
 
+protected:
+  char *PlugSubAllocStr(PGLOBAL g, void *memp, const char *str, size_t length)
+  {
+    char *ptr;
+    if (!(ptr= (char*) PlugSubAlloc(g, memp, length + 1)))
+      return NULL;
+    memcpy(ptr, str, length);
+    ptr[length]= '\0';
+    return ptr;
+  }
 public:
   ha_connect(handlerton *hton, TABLE_SHARE *table_arg);
   ~ha_connect();