Replace uses of std::iswdigit() with FXSYS_IsDecimalDigit().

Change-Id: Ide6f5c2f17468bfa953df0961303980fbc6e8956
Reviewed-on: https://pdfium-review.googlesource.com/c/46770
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/core/fxcrt/widestring.cpp b/core/fxcrt/widestring.cpp
index 49f82a6..7dc0d21 100644
--- a/core/fxcrt/widestring.cpp
+++ b/core/fxcrt/widestring.cpp
@@ -77,7 +77,7 @@
     }
     if (nWidth == 0) {
       nWidth = FXSYS_wtoi(pStr);
-      while (std::iswdigit(*pStr))
+      while (FXSYS_IsDecimalDigit(*pStr))
         ++pStr;
     }
     if (nWidth < 0 || nWidth > 128 * 1024)
@@ -90,7 +90,7 @@
         pStr++;
       } else {
         nPrecision = FXSYS_wtoi(pStr);
-        while (std::iswdigit(*pStr))
+        while (FXSYS_IsDecimalDigit(*pStr))
           ++pStr;
       }
     }