[NaCl SDK] Switch ppapi_simple to C library

native_client_sdk/src/libraries/ppapi_simple/library.dsc

 {
   'TOOLS': ['bionic', 'newlib', 'glibc', 'pnacl', 'linux', 'mac', 'clang-newlib'],
   'TARGETS': [
     {
       'NAME' : 'ppapi_simple',
       'TYPE' : 'lib',
       'SOURCES' : [
-        "ps.cc",
-        "ps_context_2d.cc",
-        "ps_event.cc",
-        "ps_instance.cc",
-        "ps_interface.cc",
-        "ps_main.cc",
+        "ps.c",
+        "ps_context_2d.c",
+        "ps_event.c",
+        "ps_instance.c",
+        "ps_interface.c",
+        "ps_main.c",
+        "ps_entrypoints_c.c"
       ],
-    }
+    },
   ],
   'HEADERS': [
     {
       'FILES': [
         "ps.h",
         "ps_context_2d.h",
         "ps_event.h",
         "ps_instance.h",
         "ps_interface.h",
         "ps_main.h",
       ],
       'DEST': 'include/ppapi_simple',
     },
   ],
   'DEST': 'src',
   'NAME': 'ppapi_simple',
 }