datatoc: exclude the initial C-style comment from GLSL/MSL/Cuda files

Add optional argument `STRIP_LEADING_C_COMMENTS` to CMake macros:
data_to_c_simple & data_to_c.

Strip leading C-style comments that don't bloat binary size.
Comments are replaced with blank lines so line numbers in error messages
match. Reduces Blender's binary size by ~70kb.

intern/opensubdiv/CMakeLists.txt

@@ -87,7 +87,11 @@ if(WITH_OPENSUBDIV)
     add_definitions(-D_USE_MATH_DEFINES)
   endif()
 
-  data_to_c_simple(internal/evaluator/shaders/glsl_compute_kernel.glsl SRC)
+  data_to_c_simple(
+    internal/evaluator/shaders/glsl_compute_kernel.glsl
+    SRC
+    STRIP_LEADING_C_COMMENTS
+  )
 else()
   list(APPEND SRC
     stub/opensubdiv_stub.cc