PostgreSQL libpq undersizes allocations, via integer wraparound

Integer wraparound in multiple PostgreSQL libpq client library functions allows an application input provider or network peer to cause libpq to undersize an allocation and write out-of-bounds by hundreds of megabytes. This results in a segmentation fault for the application using libpq. Versions before PostgreSQL 18.1, 17.7, 16.11, 15.15, 14.20, and 13.23 are affected.