BBVS: Silence double->float conversion warning.

This might not be obvious to a C++ developer, but we use C's sin which is
*always* double. Thus, sin will return a double and therefore some compilers
might warn about this conversion.
BBVS: Use floating point constants of type float.
AVALANCHE: Make GraphicManager::drawArc code consistently use float.

I use float over double here because all the changing values were already
stored in variables of type float. This also silences some float conversion
warnings.
MOHAWK: Use float constants in Myst code.

This silences some float conversion warnings.
SWORD25: Use float constant values in expressions which result in float.

This silences some float conversion warnings.
COMMON: Make Rad<->Deg conversion use float constants.

Since we take a float parameter and return a float value we will also just
work on float values all the way. This silences some float conversion
warnings.
COMMON: Use float constants in RDFT code.

We use float types in variables, thus also use them for constants. Silences
some conversion warnings.
COMMON: Some formatting fixes in RDFT code.
SCI: Silence double to float conversion warning.
COMMON: Use float constants in DCT code.

Makes the DCT code use constants of type float in expressions which only use
type float values otherwise. This silences some floating point conversion
warnings in the DCT code.