Update modulefinder to compile on riscv

This is in response to CodeQL security scan alert #1-#3.

`Elf[32|64]_Ehdr[.e_phnum|.e_phentsize|.e_shnum|.e_shentsize]` are all `uint16_t`, this means the loop-var `i` is bounded by `uint16_t` and should fit in a `uint32_t` (to prevent unsigned overflow in the loop). A switch to unsigned still makes sense, because we reduce the future chance of unnecessary signed overflow (=UB) in the loop body.

All program/section-header table entry sizes are cast to `uin64_t` even though the multiplication is bound to `uint32_t` by both factors being bound by `uint16_t`. This fixes the potential overflow before conversion to the bigger type.

* fix: remove a potential overflow before conversion

This is in response to CodeQL security scan alert #1-#3.

`Elf[32|64]_Ehdr[.e_phnum|.e_phentsize|.e_shnum|.e_shentsize]` are all `uint16_t`, this means the loop-var `i` is bounded by `uint16_t` and should fit in a `uint32_t` (to prevent unsigned overflow in the loop). A switch to unsigned still makes sense, because we reduce the future chance of unnecessary signed overflow (=UB) in the loop body.

All program/section-header table entry sizes are cast to `uin64_t` even though the multiplication is bound to `uint32_t` by both factors being bound by `uint16_t`. This fixes the potential overflow before conversion to the bigger type.

* also safely cast the access to section header string table.