clean up third-party files

Made the following changes to third-party/inteldfp:

- Ensure that it contains the same files as the upstream.

- Remove "EXAMPLES" and "TESTS" directories from inteldf, because they
  occupied too much space.

- Update 'wscript' to stop use "DECIMAL_GLOBAL_EXCEPTION_FLAGS".

Remove decnumber.pdf from third-party/decnumber.

Update bdldfp_decimalimputil_inteldfp.t.cpp to no longer use inteldfp
wrapper files.
Add README_BLOOMBERG to third-party packages

README_BLOOMBERG contains information about how to obtain the upstream
libraries and any changes made to the upstream libraries.
Add decPacked.c to decNumber third party library

decPacked.c was not included because it was not used by bdldfp, but the
one of the purposes of providing the third-party libraries is to allow
them to be reused by other clients who may have different requirements
compared to BDE code.
Explain which source files are used in decNumber