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.)
