Several fixes regarding OFnumeric_limits.

The initialization state of FLT_ROUNDS is now dumped to DCMTK_ROUND_STYLE
during configuration, which can then be evaluated in a compile time
context. This is necessary to conform closely enough to the C++ standard
as required by clang.
Mac OS X's special floating point exception control macros are now applied
on that platform, instead of the GNU POSIX extensions previously employed
there as well.
The existence of '_fpclassf' on the Windows platform is now probed
regarding the linker as well (previously only the compile time presence was
tested).
Use "try and catch" block around new[].

Use "try and catch" blocks in order to catch the "bad allocation" exception
thrown by the call of "new" when non-throwing new operator is not available.
Fixed error handling in detachValueField().

Fixed error handling in method detachValueField(), i.e. return an error code
in case the memory could not be allocated by new.
Fixed error handling in changeValue().

Fixed error handling in method changeValue(), i.e. return an error code in
case the memory could not be allocated by new[] or loadValue() failed.
Added new test case for VR=FD.

Added new test case for the VR class DcmFloatingPointDouble in order to make
sure that the revised version of DcmElement::changeValue(), which is e.g.
used by DcmFloatingPointDouble::putFloat64(), still works as expected.
Changed attribute used for the "FD" test.

Changed attribute used for the Floating Point Double (FD) test from Physical
Delta X (0018,602C) to Inversion Times (0018,9079) because only the latter
allows for storing multiple values (value multiplicity = 1-n).