Getting rid of more (FX_LPCWSTR) casts and fixing two bugs revealed by this.

core/src/fpdfdoc/doc_form.cpp

Index: core/src/fpdfdoc/doc_form.cpp
diff --git a/core/src/fpdfdoc/doc_form.cpp b/core/src/fpdfdoc/doc_form.cpp
index 821b9981b83f9361598facfef89d2b890a10a045..6b7e6bf2d69b4dafbb5fbc40b17fb5035d5647e0 100644
--- a/core/src/fpdfdoc/doc_form.cpp
+++ b/core/src/fpdfdoc/doc_form.cpp
@@ -161,7 +161,7 @@ CFieldTree::_Node *CFieldTree::_Lookup(_Node *pParent, const CFX_WideString &sho
     for (int i = 0; i < ptr_array.GetSize(); i ++) {
         _Node *pNode = (_Node *)ptr_array[i];
         if (pNode->short_name.GetLength() == short_name.GetLength() &&
-                FXSYS_memcmp32((FX_LPCWSTR)pNode->short_name, (FX_LPCWSTR)short_name, short_name.GetLength()*sizeof(FX_WCHAR)) == 0) {
+                FXSYS_memcmp32(pNode->short_name.c_str(), short_name.c_str(), short_name.GetLength()*sizeof(FX_WCHAR)) == 0) {
             return pNode;
         }
     }