fix warnings on Mac in src/effects

Fix these class of warnings:
- unused functions
- unused locals
- sign mismatch
- missing function prototypes
- missing newline at end of file
- 64 to 32 bit truncation

The changes prefer to link in dead code in the debug build
with 'if (false)' than to comment it out, but trivial cases
are commented out or sometimes deleted if it appears to be
a copy/paste error.
Review URL: https://codereview.appspot.com/6299049

git-svn-id: http://skia.googlecode.com/svn/trunk@4181 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/SkArithmeticMode.cpp b/src/effects/SkArithmeticMode.cpp
index 45464c2..c999ce0 100644
--- a/src/effects/SkArithmeticMode.cpp
+++ b/src/effects/SkArithmeticMode.cpp
@@ -133,6 +133,7 @@
 #endif
 }
 
+#if 0 // UNUSED
 static int32_t toDot8(SkScalar x) {
 #ifdef SK_SCALAR_IS_FIXED
     x += 1 << 7;
@@ -142,17 +143,18 @@
     return (int32_t)(x * 256);
 #endif
 }
+#endif
 
 SkXfermode* SkArithmeticMode::Create(SkScalar k1, SkScalar k2,
                                      SkScalar k3, SkScalar k4) {
     if (fitsInBits(k1, 8) && fitsInBits(k2, 16) &&
         fitsInBits(k2, 16) && fitsInBits(k2, 24)) {
 
+#if 0 // UNUSED
         int32_t i1 = toDot8(k1);
         int32_t i2 = toDot8(k2);
         int32_t i3 = toDot8(k3);
         int32_t i4 = toDot8(k4);
-#if 0
         if (i1) {
             return SkNEW_ARGS(SkArithmeticMode_quad, (i1, i2, i3, i4));
         }