Suspected implicit conversion errors

At line 524 and 526 of sqlite/src/func.c, clang10 complains that
"error: implicit conversion from 'long long' to 'double' changes value from 9223372036854775806 to 9223372036854775808
if( n==0 && r>=0 && r=0 && r LLONG_MAX)".
The source code is
```c
dbl:if (darg < LLONG_MIN || darg > LLONG_MAX)
265 luaL_error(lua, "conversion to: int failed from: %f", darg);
266 *val= (long long) darg;
267 return;
```
If darg is 9223372036854775807.5(could this happen?), there might be a risk of overflow.

Start with the reported expressions in sqlite/src/func.c at lines 524 and 526 and lua/ltypes.c around line 264, then compare the referenced SQLite commit. Reproduce the clang10 implicit-int-float-conversion diagnostics and determine whether the reported boundary values can overflow; done means the affected code builds without these errors and the conversion behavior is addressed.

Written by the indexing model from the issue text.