libdfp: Rewrite fpclassify to use libdecnumber

This patch refactor fpclassifyd[32|64|128] implementation to use
libdecnumber and avoid internal DPD logic in default implementation.
It also adds more FP_ZERO tests.
Initial BID support (WIP)

This patch adds initial bid support for libdfp.  It is mainly a build
enablement, the transformation routines for BID to decNUmber are empty.
It setup the build infraestructure, move the common files for default
paths and add the BID specific files.
Test get digits improved.

The test test-get_digits was improved with more cases and now it tests
64 bits and 128 bits as well.
Functions _get_digits for BID decoding developed.

The functions decoding BID numbers were developed.
libdfp: Fix symbol-hacks paths for BID and DPD
Test get digits use the correct encoding.

The test-get_digits was using only DPD encoding, now it identifies
which data format it should use.
libdpf: Fix sign compare compiler warning
libdecnumber: Cleanup symbol names

This patch removes the decimal[32|64|128]Symbol.h headers to cleanup
up the symbol names.  This removes the internal rename of symbol that
adds the '___' prefix (which is not really necessary for libdfp).
libcecnumber: decNumberSymbols.h name cleanup

This patch removes the decNumberSymbols.h header which redefines
libdecnumber internal symbols by preprending them with "___" string.
libdfp: decContextSymbols names cleanup

This patch remove the symbol redefinition header decContextSymbols.h
from libdecnumber and adjust the functions that calls its functions.
libdfp: libdecnumber symbol name cleanup

This patch remove more uneeded symbol redefinition headers.  More
specifically decCommonSymbols.h, decDPDSymbols.h, decDoubleSymbols.h,
decPackedSymbols.h, decQuadSymbols.h, and decSingleSymbols.h.
libdfp: Use libdecnumber compare on ilogbd

This patch changes the way to find which rounding to use by using
libdecnumber compare instruction instead of the compiler generate
compare instructions.
libdecnumber: Move common definition under DPD

This patch moves headers with common decimal defintions (range,
exponent, etc.) to libdecnumber common folder.  This is to avoid the
need to duplicate it on bid folder and also to organize headers better.
libdecnumber: Move common debug directive to common header

This patch moves the implementation of decNumberShow to a common header.
libdecnumber: Add initial BID support for _Decimal64

This patch add Binary Integer Decimal encoding support on libdecnumber
for _Decimal64 type.  All libdfp tests now pass, with some exceptions
due ULPs issues (since x86_64 does not have a ULP tests file).
Merge branch 'master-x86-bid' into rzinsly-x86-bid

Conflicts:
	libdecnumber/bid/decimal128.h
	libdecnumber/bid/decimal32.h
	libdecnumber/bid/decimal32Symbols.h
	libdecnumber/bid/decimal64.c
	libdecnumber/bid/decimal64.h
	sysdeps/soft-dfp/bid/numdigits.h