CritBit: use type bit fields to allow unions
block_allocator: use valgrind macros
fix stralloc in DO_PIKE_CLEANUP
call_with_interpreter: rereset Pike_interpreter_pointer to zero in debug
mode
Image.BMP: zero padding bytes when running with valgrind support
encode_value: Support variant functions.

Note: No changes were needed to decode_value().
MasterObject: Implement getenv() with variants.
Image.Webp: do not read outside of buffer