crt: iswblank: remove explicit check for L'\t'

mingw-w64 now provides `iswctype` function which properly handles TAB character;
this allows to remove explicit check for L'\t' in both library and macro
versions of `iswblank` function.

Signed-off-by: Kirill Makurin <maiddaisuki@outlook.com>
Signed-off-by: LIU Hao <lh_mouse@126.com>

mingw-w64-crt/misc/iswblank.c

diff --git a/mingw-w64-crt/misc/iswblank.c b/mingw-w64-crt/misc/iswblank.c
index dc48c29..7db31de 100644
--- a/mingw-w64-crt/misc/iswblank.c
+++ b/mingw-w64-crt/misc/iswblank.c
@@ -3,6 +3,10 @@
 
 int __cdecl iswblank (wint_t _C)
 {
-  return (iswctype(_C, _BLANK) || _C == '\t');
+  /**
+   * mingw-w64's `iswctype` is a wrapper around CRT's `iswctype` which
+   * properly handles TAB character.
+   */
+  return iswctype (_C, _BLANK);
 }
 int (__cdecl *__MINGW_IMP_SYMBOL(iswblank))(wint_t) = iswblank;

mingw-w64-headers/crt/corecrt_wctype.h

diff --git a/mingw-w64-headers/crt/corecrt_wctype.h b/mingw-w64-headers/crt/corecrt_wctype.h
index 33798b2..bed41be 100644
--- a/mingw-w64-headers/crt/corecrt_wctype.h
+++ b/mingw-w64-headers/crt/corecrt_wctype.h
@@ -77,7 +77,7 @@
 #if !defined(_CTYPE_DISABLE_MACROS) && !defined(__cplusplus)
 #define iswalnum(_c)  (iswctype(_c,_ALPHA|_DIGIT))
 #define iswalpha(_c)  (iswctype(_c,_ALPHA))
-#define iswblank(_c)  (((_c) == '\t') || iswctype(_c,_BLANK))
+#define iswblank(_c)  (iswctype(_c,_BLANK))
 #define iswcntrl(_c)  (iswctype(_c,_CONTROL))
 #define iswdigit(_c)  (iswctype(_c,_DIGIT))
 #define iswgraph(_c)  (iswctype(_c,_PUNCT|_ALPHA|_DIGIT))