[Piglit] glsl-const-builtin-*: Fix GLSL compilation errors on Mac OS X.

[Vinson Lee]

> -----Original Message-----
> From: Ian Romanick [mailto:idr at freedesktop.org]
> 
> I believe that commit 14277414 is not correct.  As far as I can tell, in
> GLSL 1.20 the call 'acos(1)' should automatically convert the int(1) to
> float(1.0).  Page 20 (26 of the PDF) of the GLSL 1.20 spec lists an
> implicit conversion for int->float.  Page 43 (49 of the PDF) says:
> 
>     "Otherwise, if no exact match is found, then the implicit
>     conversions in Section 4.1.10 "Implicit Conversions" will
>     be applied to the calling arguments if this can make their
>     types match a signature."
> 
> If Apple's compiler doesn't compile this code, then it's a bug in their
> compiler.
> 
> On a side note, those aren't very good execution tests anyway.  All of
> them will produce "correct" results even if the value generate for the
> 'one' variable is 6.02e23 due to clamping of color outputs to [0,1].