get iOS building again

1) Disable SampleApp.  Seems like it's totally horked?  SkOSFile_iOS.mm is missing about half the functions needed, and SkOSFile_stdio.cpp is double-providing the others.

2) Drop armv6.

3) Switch from putting headers in sources to putting the corresponding directories in includes.

4)  Force cast the type of glShaderSource.  Something to do with GR_GL_USE_NEW_SHADER_SOURCE_SIGNATURE?

After all this,
    env CC=clang CXX=clang++ GYP_DEFINES=skia_os=ios make
builds for me.
BUG=skia:2363
R=bsalomon@google.com, epoger@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/226413005

git-svn-id: http://skia.googlecode.com/svn/trunk@14069 2bbb7eff-a529-9590-31e7-b0007b416f81
6 files changed