Rewrite 'rationalize' to fix bugs and improve efficiency.

Fixes <http://bugs.gnu.org/14905>.
Reported by Göran Weinholt <goran@weinholt.se>.

* libguile/numbers.c (scm_rationalize): Rewrite.  Previously an
  incorrect algorithm was used which failed in many cases.

* test-suite/tests/numbers.test (rationalize): Add tests.
Fix minor formatting error in 'rationalize'.

* libguile/numbers.c (scm_rationalize): Fix formatting.
Fix incorrect rationalize tests.

* test-suite/tests/fractions.test (fractions): Fix rationalize tests.
Optimize R6RS bitwise operators.

* module/rnrs/arithmetic/bitwise.scm (bitwise-if, bitwise-length,
  bitwise-first-bit-set, bitwise-bit-field, bitwise-reverse-bit-field):
  Replace these with aliases to the identical SRFI-60 operators
  'bitwise-if', 'integer-length', 'first-set-bit', 'bit-field', and
  'reverse-bit-field'.

  (bitwise-copy-bit, bitwise-copy-bit-field, bitwise-rotate-bit-field):
  Reimplement these based upon the similar SRFI-60 operators 'copy-bit',
  'copy-bit-field', and 'rotate-bit-field'.

* test-suite/tests/r6rs-arithmetic-bitwise.test (bitwise-copy-bit): Fix
  test to conform to the specification, which requires the third
  argument to be either 0 or 1.

* test-suite/tests/r6rs-arithmetic-fixnums.test (fxcopy-bit): Fix test
  to conform to the specification, which requires the third argument to
  be either 0 or 1.
Add 'scm_i_from_double' and use it.

* libguile/numbers.c (scm_i_from_double): New static function.
  (scm_from_double): Just call 'scm_i_from_double'.
  (scm_inf, scm_nan, scm_abs, scm_i_inexact_floor_quotient,
  scm_i_inexact_floor_remainder, scm_i_inexact_floor_divide,
  scm_i_inexact_ceiling_quotient, scm_i_inexact_ceiling_remainder,
  scm_i_inexact_ceiling_divide, scm_i_inexact_truncate_quotient,
  scm_i_inexact_truncate_remainder, scm_i_inexact_truncate_divide,
  scm_i_inexact_centered_quotient, scm_i_inexact_centered_remainder,
  scm_i_inexact_centered_divide, scm_i_inexact_round_quotient,
  scm_i_inexact_round_remainder, scm_i_inexact_round_divide,
  scm_max, scm_min, scm_sum, scm_difference, scm_product,
  scm_divide, scm_truncate_number, scm_round_number, scm_floor,
  scm_ceiling, scm_expt, scm_sin, scm_cos, scm_tan, scm_sinh,
  scm_cosh, scm_tanh, scm_asin, scm_acos, scm_atan, scm_sys_asinh,
  scm_sys_acosh, scm_sys_atanh, scm_real_part, scm_imag_part,
  scm_magnitude, scm_angle, scm_exact_to_inexact, log_of_shifted_double,
  log_of_fraction, scm_log10, scm_exp, scm_sqrt, scm_init_numbers):
  Use 'scm_i_from_double' instead of 'scm_from_double'.
VM: Redefine INUM_MIN and INUM_MAX without assumptions.

* libguile/vm-i-scheme.c (INUM_MIN, INUM_MAX): Redefine to avoid
  assumptions about the representation of inums.
VM: Avoid signed overflows in 'add1' and 'sub1'.

* libguile/vm-i-scheme.c (INUM_STEP): New macro.
  (add1, sub1): Avoid signed overflows, and use INUM_STEP.
VM: Avoid overflow in ASM_ADD when the result is most-positive-fixnum.

* libguile/vm-i-scheme.c (ASM_ADD): Remove the tag from one of the
  operands before adding, to avoid overflow when the result is the most
  positive fixnum.
VM: Add "cc" to the clobber list of ASM_ADD and ASM_SUB.

* libguile/vm-i-scheme.c (ASM_ADD, ASM_SUB): Add "cc" to the clobber
  list.  Suggested by Göran Weinholt <goran@weinholt.se>.
VM: Support 32-bit x86 in ASM_ADD and ASM_SUB.

* libguile/vm-i-scheme.c (_CX): New macro.
  (ASM_ADD, ASM_SUB): Replace references to "rcx" with _CX.
VM: Add ASM_MUL for x86.

* libguile/vm-i-scheme.c (ASM_MUL): New macro.
  (mul): Use ASM_MUL if available.
VM: Avoid untagging inums in 'logand' and 'logior'.

* libguile/vm-i-scheme.c (logand, logior): Avoid untagging.
VM: Implement ASM_ADD, ASM_SUB, and ASM_MUL for ARM processors.

* libguile/vm-i-scheme.c (ASM_ADD, ASM_SUB, ASM_MUL): Implement for ARM.
VM: Define ASM_MUL on ARM only if SMULL instruction is supported.

* libguile/vm-i-scheme.c (ASM_MUL): Define only if the target
  architecture is known to implement the SMULL instruction.
VM: ASM_ADD and ASM_SUB for x86: clobber _CX not "rcx".

* libguile/vm-i-scheme.c (ASM_ADD, ASM_SUB): Clobber _CX not "rcx".
Import 'copysign' and 'isfinite' modules from Gnulib.

* lib/Makefile.am:
* m4/gnulib-cache.m4:
* m4/gnulib-comp.m4: Add 'copysign' and 'isfinite' Gnulib modules.
Use Gnulib's 'copysign' in numbers.c.

* libguile/numbers.c (double_is_non_negative_zero): Remove.
  (idbl2str, scm_max, scm_min, scm_angle, log_of_shifted_double,
  scm_log10): Use 'copysign' to check signs of zeroes,
  instead of 'double_is_non_negative_zero'.
Use Gnulib's 'isfinite' in numbers.c.

* libguile/numbers.c (DOUBLE_IS_FINITE, DOUBLE_IS_POSITIVE_INFINITY,
  DOUBLE_IS_NEGATIVE_INFINITY): Remove.
  (scm_odd_p, scm_even_p, scm_finite_p, icmplx2str, scm_rational_p,
  scm_inexact_to_exact): Use 'isfinite' instead of 'DOUBLE_IS_FINITE'.
VM: ash: Use SCM_SRS and handle large right shift in fast path.

* libguile/vm-i-scheme.c (ash): Use SCM_SRS.  Handle inum right shift by
  more than SCM_I_FIXNUM_BIT-1 bits in fast path.
RTL VM: ash: Use SCM_SRS and fix large right shifts in fast path.

* libguile/vm-engine.c (ash): Use SCM_SRS, and handle large right
  shifts properly.