Since stdint.h was added in C99, pass the required C standard to the
compiler explicitly, and do the same for C++ standard along the way.

As we're using std int types (since previous commit), use corresponding std
format macros to avoid potential format specifier mismatches.

MSDN states that SSIZE_T is defined as LONG_PTR, and LONG_PTR is defined as
long (32-bit) when building for x86 and __int64 (64-bit) when building for
x64, which basically means that it's signed and its size matches that of a
pointer, which in turn is the definition of intptr_t. The latter is
provided by stdint.h which we're already including.

This avoids potential clashes as the name is way too common.

This avoids potential clashes as the name is way too common.

This avoids potential clashes as the name is way too common.

This avoids potential clashes as the name is way too common.

This header is C99 and we can use it since we're already using stdint.h and
inttypes.h anyway. It also helps to avoid clashes when other code that uses
this library includes stdbool.h.

Most probably not all the places were covered, some more work (unrelated to
these changes) needs to be done.