Add overrides and switch to nullptr keyword for all files

Adds remaining missing overrides and nullptr usages, missed due to
an extreme failure in tool usage.

Change-Id: I56abd72975a3999ad13330003c348db40f59aebf
diff --git a/libs/hwui/Program.cpp b/libs/hwui/Program.cpp
index e6fd2dc..fb07dfa 100644
--- a/libs/hwui/Program.cpp
+++ b/libs/hwui/Program.cpp
@@ -64,7 +64,7 @@
                 glGetProgramiv(mProgramId, GL_INFO_LOG_LENGTH, &infoLen);
                 if (infoLen > 1) {
                     GLchar log[infoLen];
-                    glGetProgramInfoLog(mProgramId, infoLen, 0, &log[0]);
+                    glGetProgramInfoLog(mProgramId, infoLen, nullptr, &log[0]);
                     ALOGE("%s", log);
                 }
                 LOG_ALWAYS_FATAL("Error while linking shaders");
@@ -135,7 +135,7 @@
     ATRACE_NAME("Build GL Shader");
 
     GLuint shader = glCreateShader(type);
-    glShaderSource(shader, 1, &source, 0);
+    glShaderSource(shader, 1, &source, nullptr);
     glCompileShader(shader);
 
     GLint status;
@@ -145,7 +145,7 @@
         // Some drivers return wrong values for GL_INFO_LOG_LENGTH
         // use a fixed size instead
         GLchar log[512];
-        glGetShaderInfoLog(shader, sizeof(log), 0, &log[0]);
+        glGetShaderInfoLog(shader, sizeof(log), nullptr, &log[0]);
         LOG_ALWAYS_FATAL("Shader info log: %s", log);
         return 0;
     }