The method accepts strings with numbers in scientific or normal notation,
e.g. -1.25 or 3.37e-6. The numeric range is limited by the sr_rational
range, i.e +-9.2e18, resolution is ~19 digits.
Since Autoconf places some important feature flags only into the
configuration header, it is necessary to include it globally to
guarantee a consistent build.
Stefan Brüns
Gerhard Sittig
Daniel Elstner
Uwe Hermann