Fix bslmf_enableif bdeverify warnings and test driver

The usage example for bslmf_enableif is making qualified use of 'std::size_t'
without including the necessary header, <cstddef>.  This applies to only one
usage example though, as the rest of the code uses the unqualified 'size_t'
introduced correctly via the header <stddef.h>.  This issue shows up as a
transitive header dependency only on Windows, and recent gcc on Solaris
builds.

Fixed by dropping the explicit 'std::' qualification.

In addition, upgraded the component to cleanly pass the current version of
the 'bde_verify' tool, which included silencing a few warnings around the
usage examples with #prgama bde_verify.  Double-checked with bdespell and
bdeflag for any remaining issues, while discarding false positives.
Fix ASSERT->assert for usage example
Restore earlier usage example edits for bslmf_enableif

It appears an eariler round of doc fixes updated the usage examples for 'bslmf::enable_if',
but did not make corresponding changes to the test driver.  The last round of edits fixed
up issues in the test driver, and then overwrote the whole usage example in the header,
losing the previous fixes that had no propagated back to the test.  This showed up in the
phabricator review.

This change set tries to merge the best of both worlds from both sets of edits, and to
bring the .t.cpp and the .h usage examples back into synch.
Final fixup of enable_if usage example

Final clean-up (I hope) based on diffs that are visible through phabricator.
Remove bad SUNWCCh file

This file is a relic of backwards support for non-standard headers
exposing the standard library in the global namespace.  We do not
want to push that into the open source world, and the file exists
only as a special Sun override that we missed in clean-up.
Publication of the Decimal Floating Point package.

The bdldfp package provides floating point numbers using a decimal
base, rather than a binary base.  This type can be used to better
maintain precision in certain applications.
Fixes to case & spacing nits in bdl+decnumber.txt

BDL packages get named in all miniscule (not majescule) letters
for documentation.  Fixed full-stop spacing too.
Added a source-download pointer for decNumber.

To help document decNumber's origin, I've added a link to the
download section of the decNumber website.
Jettisoned non-normative documentation files.

These files come from the decNumber library, and our process of
integration with the BDE/BDL/BSL package infrastructure.  They are
no longer needed.
Added the bdl+decnumber library to bdl package doc

The bdl+decnumber library adds no levels to the physical dependency
graph.  It depends only upon bdls for package-level source control
macros.
Added bdldfp package to the bdl package group doc.

Bdldfp provides Decimal Floating Point support.  Package group
documentation now notes its existence.
Updated bdldfp package doc to acknowledge uint128

The 'Uint128' type provides a component that is used by Decimal
Floating Point components to manipulate 128-bit blocks.  Package
doc is updated to note its existence.
Merge branch 'bdldfp-publish-fixes' into bdldfp-landing
[APPROVAL] review/bdldfp-landing to master
[APPROVAL] pending/master/fix_bslmf_enable_if_test_driver_drqs50528838 to master
Merge branch 'review/FAST_remove_non_std_istream_h_on_sun_drqs47831855'
Improve BSL-to-BDE move text.
Fix Markdown syntax
[APPROVAL] update-bsl-redirect-language-drqs-49952150 to master