[ 1181301 ] make float packing copy bytes when they can

which hasn't been reviewed, despite numerous threats to check it in
anyway if noone reviews it.  Please read the diff on the checkin list,
at least!

The basic idea is to examine the bytes of some 'probe values' to see if
the current platform is a IEEE 754-ish platform, and if so
_PyFloat_{Pack,Unpack}{4,8} just copy bytes around.

The rest is hair for testing, and tests.

refactoring to get all the duplicates of this delicate code out of the
cPickle and struct modules.

Thanks to Skip Montanaro and Kalle Svensson for the patches.

Repair float constructor to return a true float when passed a subclass
instance.  New PyFloat_CheckExact macro.

Store floats and doubles to full precision in marshal.
Test that floats read from .pyc/.pyo closely match those read from .py.
Declare PyFloat_AsString() in floatobject header file.
Add new PyFloat_AsReprString() API function.
Document the functions declared in floatobject.h.

This should match the situation in the 1.6b1 tree.

messages for specific changes.

use the new names exclusively, and the linker will see the new names.
Files that import "Python.h" also only see the new names.  Files that
import "allobjects.h" will continue to be able to use the old names,
due to the inclusion (in allobjects.h) of "rename2.h".

object.h: made sizes and refcnts signed ints.
stringobject.h: make getstrsize() signed int.
methodobject.h: add METH_VARARGS and METH_FREENAME flag bit definitions.

* Makefile: change location of FORMS library.
* posixmodule.c: turn #if 0 into #ifdef MSDOS (stuff in unistd.h or not)
* Almost all .h files: added CPP magic to avoid duplicate inclusions and
  to support inclusion from C++.

* Stubs for faster implementation of local variables (not yet finished)
* Added function name to code object.  Print it for code and function
  objects.  THIS MAKES THE .PYC FILE FORMAT INCOMPATIBLE (the version
  number has changed accordingly)
* Print address of self for built-in methods
* New internal functions getattro and setattro (getattr/setattr with
  string object arg)
* Replaced "dictobject" with more powerful "mappingobject"
* New per-type functio tp_hash to implement arbitrary object hashing,
  and hashobject() to interface to it
* Added built-in functions hash(v) and hasattr(v, 'name')
* classobject: made some functions static that accidentally weren't;
  added __hash__ special instance method to implement hash()
* Added proper comparison for built-in methods and functions