v3.5.9: Another way to derive floatofintu from floatofint

It supports a branch-free implementation of floatofintu.
Not used yet in any of the ports.

v3.5.8: Revised specification of NaN payload behavior

When an FP arithmetic instruction produces a NaN result, the payload
of this NaN depends on the architecture.

Before, the payload behavior was specified by 3 architecture-dependent
parameters: `Archi.choose_binop_pl_64` and `Archi.choose_binop_pl_32`
and `Archi.fpu_results_default_qNaN`.  This was adequate for
two-argument operations, but doesn't extend to FMA.

In preparation for FMA support, this commit generalizes the `Archi.choose`
functions from two arguments to any number of arguments.  In passing,
`Archi.fpu_results_default_qNaN` is no longer needed.

v3.5.7

More precise description of '-O0' and 'non-linear-cond-expr'

v3.5.6

Update synonymous list for -O0, add new named warning class

v3.5.5

Change the expected types for arguments to __builtin_annot, and exten…

v3.5.4

Added Pfmovite to list of known mnemonic names.

v3.5.3: Provide a float select operation for PowerPC. (#173)

The FP select for PowerPC stores both addresses in two
subsequent stack slots and loads them using an offset created
from the result of the comparison.

v3.5.2: Add a check for the args of unprototyped calls.

The arguments that are passed to an unprototyped function must
also be checked to be valid types passed to a function, i.e. they
must be complete types after argument conversion.

v3.5.1: Prepend $(DESTDIR) to the installation target (#169)

Following the gnu Makefile Conventions the variable $(DESTDIR)
should be prepended to all installation commands. This allows
staged installs.

v3.2.12: String literals are l-values and have array types (#116)

* Allow strings literals as lvalues.

Strings and WStrings literals are lvalues, thus it is allowed to take their
addresses.

Bug 23356.

* String literals have types "array of (wide) char", not "pointer to (wide) char"

The pointer types were a leftover from the early, CIL-based C frontend.

* Remove special case for sizeof("string literal") during elaboration

No longer needed now that literals have array types.