Use the fallback implementation for lround() only on pre-2013 Visual
Studio, and ensure we are clear about the types of the parameters for
lround() and scalbnf(), since Visual Studio can be quite picky on
ambiguous parameter types. Also, use g_ascii_strcasecmp() rather than
strcasecmp() as we are already using GLib for this code and we are
assured that g_ascii_strcasemp() is available.
For scalbnf() on pre-2013 Visaul Studio, a fallback implementation is
needed, but use another forced-included header for those compilers, which
will be added later.
Also use (char)27 on Visual Studio builds as '\e' is not a recognized
escape sequence, which will do the same thing.
