Previously, each warning suppression was self-contained, with its
own pair of `SUPPRESS_X_WARNING` and `UNSUPPRESS_X_WARNING` macros.
This had the obvious advantage of being self-containing, but it
also meant that if we needed to suppress more than one warning
in a single place, then we would manipulate the compiler's warning
state multiple times, even though logically we would only need one
layer.

The new way of suppressing warnings in macros is to push compiler's
warning state with `CATCH_INTERNAL_START_WARNINGS_SUPPRESSION` macro,
then disable whatever macros we need with the
`CATCH_INTERNAL_SUPPRESS_X_WARNINGS` macro, and then return to the
previous state using `CATCH_INTERNAL_STOP_WARNINGS_SUPPRESSION`.

This should now properly handle small numbers which would previously
output something like `[0.00000000000000019, 0.00000000000000019]`,
which does not allow user to read the numbers properly.

Closes #1760

Only works for exceptions that publicly derive from `std::exception`
and the matching is done exactly, including case and whitespace.

Closes #1649
Closes #1728

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It checks Knuth's _close enough with tolerance_ relationship, that
is `|lhs - rhs| <= epsilon * max(|lhs|, |rhs|)`, rather then the
_very close with tolerance_ relationship that can be written down as
`|lhs - rhs| <= epsilon * min(|lhs|, |rhs|)`.

This is because it is the more common model around the internet, and
as such is likely to be less surprising to the users. In the future
we might want to provide the other model as well.

Closes #1746