Normalize GL_UNPACK_ALIGNMENT

Several places were setting GL_UNPACK_ALIGNMENT
unneccessarily, whereas other places were assuming an
unpack alignment of 1. Since we never actually
do explicit row-alignment, set GL_UNPACK_ALIGNMENT
to 1 at context creation time and never change it

Bug: 26584230

Also turns on aggressive glGetError checking to
better catch potential problem zones

Change-Id: I190c8f0f0494a7f046d5ed769405c75d363be59a
diff --git a/libs/hwui/BakedOpRenderer.cpp b/libs/hwui/BakedOpRenderer.cpp
index 0931282..e65746e 100644
--- a/libs/hwui/BakedOpRenderer.cpp
+++ b/libs/hwui/BakedOpRenderer.cpp
@@ -139,9 +139,7 @@
     mCaches.pathCache.trim();
     mCaches.tessellationCache.trim();
 
-#if DEBUG_OPENGL
-    GLUtils::dumpGLErrors();
-#endif
+    GL_CHECKPOINT();
 
 #if DEBUG_MEMORY_USAGE
     mCaches.dumpMemoryUsage();