Globally disable MSVC warning 4201 (nonstandard extension nameless struct)

...it is caused by some external code (newly so by glm included in chart2) and
does not really add value.  (Incidentally, all relevent compilers, Clang, GCC,
and MSVC uniformly support this language extension anyway.)

Change-Id: I5b4c11b5cea0267bf39ac95e9021a5761a4d7b91
Fix various MSVC warnings in new chart2 OpenGL code

Change-Id: I5de9020f42004e21b58b9d2ef5d41b5338da43ba