Fix compilation with Firebird < 3

ext/pdo_firebird/firebird_statement.c

@@ -229,9 +229,11 @@ static int firebird_stmt_describe(pdo_stmt_t *stmt, int colno) /* {{{ */
 #endif
 				col->param_type = PDO_PARAM_INT;
 				break;
+#ifdef SQL_BOOLEAN
 			case SQL_BOOLEAN:
 				col->param_type = PDO_PARAM_BOOL;
 				break;
+#endif
 			default:
 				col->param_type = PDO_PARAM_STR;
 				break;
@@ -419,11 +421,13 @@ static int firebird_stmt_get_col(pdo_stmt_t *stmt, int colno, char **ptr,  /* {{
 					*ptr = FETCH_BUF(S->fetch_buf[colno], char, CHAR_BUF_LEN, NULL);
 					*len = slprintf(*ptr, CHAR_BUF_LEN, "%F" , *(double*)var->sqldata);
 					break;
+#ifdef SQL_BOOLEAN
 				case SQL_BOOLEAN:
 					*len = sizeof(zend_bool);
 					*ptr = FETCH_BUF(S->fetch_buf[colno], zend_bool, 1, NULL);
 					*(zend_bool*)*ptr = *(FB_BOOLEAN*)var->sqldata;
 					break;
+#endif
 				case SQL_TYPE_DATE:
 					isc_decode_sql_date((ISC_DATE*)var->sqldata, &t);
 					fmt = S->H->date_format ? S->H->date_format : PDO_FB_DEF_DATE_FMT;