Revert "Merge pull request KhronosGroup#301 from alan-baker/hpp1" (KhronosGroup#302)

This reverts commit 747031e, reversing
changes made to 85a1ed2.

In other words, don't add the .hpp11 files to the BUILD.gn
That's because GN doesn't recognize .hpp11 extension as a C/C++
header file.

See https://bugs.chromium.org/p/gn/issues/detail?id=311

Instead, client dependencies should #include the .hpp11 file directly
even though that seems to hide it away from GN's visibility.
That seems wrong, but it does work.

Author: dneto0

BUILD.gn

@@ -32,14 +32,12 @@ source_set("spv_headers") {
     "include/spirv/1.2/OpenCL.std.h",
     "include/spirv/1.2/spirv.h",
     "include/spirv/1.2/spirv.hpp",
-    "include/spirv/1.2/spirv.hpp11",
     "include/spirv/unified1/GLSL.std.450.h",
     "include/spirv/unified1/NonSemanticClspvReflection.h",
     "include/spirv/unified1/NonSemanticDebugPrintf.h",
     "include/spirv/unified1/OpenCL.std.h",
     "include/spirv/unified1/spirv.h",
     "include/spirv/unified1/spirv.hpp",
-    "include/spirv/unified1/spirv.hpp11",
   ]
 
   public_configs = [ ":spv_headers_public_config" ]