Substitute in nasm64developer's "acfloat4" routine. This
floating-point conversion routine is not perfect (it gets a fair
number of LSB errors), but the old NASM code was just plain broken.
nasm64developer's code at least gets within ±1 LSB.
Both C and C++ have "bool", "true" and "false" in lower case; C
requires <stdbool.h> for this, in C++ it is an inherent type built
into the compiler. Use those instead of the old macros; emulate with
a simple typedef enum if unavailable.
Concentrate compiler dependencies to compiler.h; make sure compiler.h
is included first in every .c file (since some prototypes may depend
on the presence of feature request macros.)
Actually use the conditional inclusion of various functions (totally
broken in previous releases.)
Unify all the standard IEEE formats into one function, add support for
IEEE standard 128-bit floating point numbers.
The 80-bit format is still special since it explicitly represents the
integer portion.
