Get rid of most instance of 'foo == NULL'

core/src/fxcrt/fx_basic_gcc.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include <limits>
 #include <cctype>
 #include <cwctype>
 
@@ skipping 102 matching lines @@
 extern "C" {
 #endif
 int FXSYS_GetACP() {
   return 0;
 }
 FX_DWORD FXSYS_GetFullPathName(const FX_CHAR* filename,
                                FX_DWORD buflen,
                                FX_CHAR* buf,
                                FX_CHAR** filepart) {
   int srclen = FXSYS_strlen(filename);
-  if (buf == NULL || (int)buflen < srclen + 1) {
+  if (!buf || (int)buflen < srclen + 1) {
     return srclen + 1;
   }
   FXSYS_strcpy(buf, filename);
   return srclen;
 }
 FX_DWORD FXSYS_GetModuleFileName(void* hModule, char* buf, FX_DWORD bufsize) {
   return (FX_DWORD)-1;
 }
 #ifdef __cplusplus
 }
 #endif
 #endif
 #if _FXM_PLATFORM_ != _FXM_PLATFORM_WINDOWS_
 #ifdef __cplusplus
 extern "C" {
 #endif
 FXSYS_FILE* FXSYS_wfopen(const FX_WCHAR* filename, const FX_WCHAR* mode) {
   return FXSYS_fopen(CFX_ByteString::FromUnicode(filename),
                      CFX_ByteString::FromUnicode(mode));
 }
 char* FXSYS_strlwr(char* str) {
-  if (str == NULL) {
+  if (!str) {
     return NULL;
   }
   char* s = str;
   while (*str) {
     *str = FXSYS_tolower(*str);
     str++;
   }
   return s;
 }
 char* FXSYS_strupr(char* str) {
-  if (str == NULL) {
+  if (!str) {
     return NULL;
   }
   char* s = str;
   while (*str) {
     *str = FXSYS_toupper(*str);
     str++;
   }
   return s;
 }
 FX_WCHAR* FXSYS_wcslwr(FX_WCHAR* str) {
-  if (str == NULL) {
+  if (!str) {
     return NULL;
   }
   FX_WCHAR* s = str;
   while (*str) {
     *str = FXSYS_tolower(*str);
     str++;
   }
   return s;
 }
 FX_WCHAR* FXSYS_wcsupr(FX_WCHAR* str) {
-  if (str == NULL) {
+  if (!str) {
     return NULL;
   }
   FX_WCHAR* s = str;
   while (*str) {
     *str = FXSYS_toupper(*str);
     str++;
   }
   return s;
 }
 int FXSYS_stricmp(const char* dst, const char* src) {
@@ skipping 62 matching lines @@
       buf[wlen] = bstr[i];
     }
     wlen++;
   }
   return wlen;
 }
 #ifdef __cplusplus
 }
 #endif
 #endif