FTBFS with GCC 13

Fails due to:

[  143s] In file included from ./symtab.ih:1:
[  143s] ./symtab.h:20:9: error: 'uint16_t' does not name a type
[  143s]    20 |         uint16_t    location;           // the variable's location
[  143s]       |         ^~~~~~~~
[  143s] ./symtab.h:8:1: note: 'uint16_t' is defined in header '<cstdint>'; did you forget to '#include <cstdint>'?
[  143s]     7 | #include "../exprtype/exprtype.h"
[  143s]   +++ |+#include <cstdint>
[  143s]     8 | 

and it's documented here: https://gcc.gnu.org/gcc-13/porting_to.html#header-dep-changes