Initial checkin of experimental bignum type.

[SVN r73607]
Add a few non-member functions for real-valued types.
Add minimal docs.

[SVN r73608]
Add some build warnings.

[SVN r73610]
Add ldexp and frexp.

[SVN r73612]
Add missing #includes.

[SVN r73626]
Add rvalue reference support.
Add LINPACK benchmark test.
Update arithmetic tests to work with types other than big_number.
Fix precision of ostream& operator<<.

[SVN r73649]
Fix code to compile with GCC.

[SVN r73660]
Change backend concepts to allow for easier default implementations, plus out-of-place arithmetic as well as in-place.
Change non-member functions to use expression templates with result value passed to the function as "workspace".

[SVN r73819]
Add some more modulus tests, fix regressions and add abs function for gmp_int backend.

[SVN r73840]
Fix buglets in GMP support, add MPFR support.

[SVN r73922]
Added new backend adapter type, plus tentative e_float support.
Added numeric_limits support, plus embryonic test program.

[SVN r74004]
Add increment, decrement and bitwise-shift operators.

[SVN r74024]
Add sign and is_zero functions.
Add use in boolean context.

[SVN r74042]
Add test cases for expression-template used in boolean context.

[SVN r74043]
Add conversion routines.
Add Jamfile.
Fix broken stream operators.

[SVN r74057]
Add bitwise integer ops.
Reorganise proto grammar.

[SVN r74089]
Change function evaluation calling convention and naming.
Add integer-powers support.

[SVN r74166]
Added fpclassify routines.

[SVN r74167]
Bring mpfr backend into line with Boost.Math's requirements.
Fix input streaming.
Add MPQ support.
Mostly fix gcc compiler issues.

[SVN r74354]
Optimise comparison to zero.
Remove unnecessary static asserts - even floats are incrementable.
Fix some of the default function methods, and add fmod.
Add mpq comparison and conversion routines.
Add mpfr lanczos support.
Add std lib function support for big_number_architype.
Update comparison tests.

[SVN r74479]