Previously code in the SWIG tool didn't handle allocation failures
well. Most places didn't check for NULL return from
malloc()/realloc()/calloc() at all, typically resulting in undefined
behaviour, and some places used assert() to check for a NULL return
(which is a misuse of assert() and such checks disappear if built with
NDEBUG defined leaving us back with undefined behaviour).
All C allocations are now done via wrapper functions (Malloc(),
Realloc() and Calloc()) which emit and error and exit with non-zero
status on failure, so a non-NULL return can be relied upon.
Fixes#1901.
e38847f7e1