[estebanzimanyi]

A MEOS function returning char * hands the caller a string the caller
owns, as MEOS's example 03_berlinmod_assemble.c frees the
temporal_as_hexwkb it writes, so
the wrapper copies it into a Python str and frees it (_take_string); a
const char * names a string MEOS keeps, such as temporal_subtype's, and
is copied alone (_read_string). A byte buffer MEOS sizes through a
size_t pointer is copied into bytes and freed the same way
(_take_bytes). A NULL return is None before any copy. The cdef declares
the C library's free beside the catalog's functions. GoMEOS frees each
char * return and leaves each const char * alone, and MEOS.NET's string
marshalling frees the string it copies.

Witness: a wrapper returning _ffi.string(result).decode(...) or
bytes(_ffi.buffer(result, size)) left the C allocation behind on every
call: 152 string returns, 48 byte buffers and text_to_cstring.

Measured: on wheels generated from one catalog of MobilityDB master
9c0caecd72, before and after, 200000 calls each grow the resident set by
15616 KB (temporal_out), 18688 KB (temporal_as_hexwkb) and 12416 KB
(temporal_as_wkb) before and by 0 KB after; the generated surfaces
differ in those returns and the three helpers alone; PyMEOS master
passes 4855 tests with 1 skipped on the wheel after, and the smoke test
reads a freed and a kept string twice each.