fix warnings on Mac in gm

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/6305046

git-svn-id: http://skia.googlecode.com/svn/trunk@4185 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/shadertext.cpp b/gm/shadertext.cpp
index b574ab6..0f2a9e9 100644
--- a/gm/shadertext.cpp
+++ b/gm/shadertext.cpp
@@ -36,7 +36,7 @@
     canvas.drawPaint(paint);
 }
 
-SkShader* MakeBitmapShader(SkShader::TileMode tx, SkShader::TileMode ty,
+static SkShader* MakeBitmapShader(SkShader::TileMode tx, SkShader::TileMode ty,
                            int w, int h) {
     static SkBitmap bmp;
     if (bmp.isNull()) {