- Refactor the existing SNMALLOC_ASSERT and SNMALLOC_CHECK. These now
use the FatalErrorBuilder to format the output if a format string is
provided.
- Extend the FatalErrorBuilder to print decimal integers for signed
values.
- Rename FatalErrorBuilder to MessageBuilder.
- Rewrite the macros used in the jemalloc tests to use
FatalErrorBuilder and move them into a header.
- Refactor some of the tests to use the new macros.