Rename CPDFDoc_Environment to CPDFSDK_Environment

CPDFDoc_Environment does not fit with the general naming scheme of the rest of
the files in fpdfsdk. This CL updates the naming to CPDFSDK_Environment to
better fit with the surrounding files.

Review-Url: https://codereview.chromium.org/2333413003
diff --git a/fpdfsdk/cfx_systemhandler.cpp b/fpdfsdk/cfx_systemhandler.cpp
index 2589565..eb9cff2 100644
--- a/fpdfsdk/cfx_systemhandler.cpp
+++ b/fpdfsdk/cfx_systemhandler.cpp
@@ -13,9 +13,9 @@
 #include "core/fxge/include/cfx_fontmgr.h"
 #include "core/fxge/include/cfx_gemodule.h"
 #include "fpdfsdk/formfiller/cffl_formfiller.h"
-#include "fpdfsdk/include/cpdfdoc_environment.h"
 #include "fpdfsdk/include/cpdfsdk_annot.h"
 #include "fpdfsdk/include/cpdfsdk_document.h"
+#include "fpdfsdk/include/cpdfsdk_environment.h"
 #include "fpdfsdk/include/cpdfsdk_pageview.h"
 
 namespace {