Mark libc ctype functions as pure where applicable.

Author: ibuclaw

src/core/stdc/ctype.d

@@ -18,17 +18,17 @@ extern (C):
 @trusted: // All of these operate on integers only.
 nothrow:
 
-int isalnum(int c);
-int isalpha(int c);
-int isblank(int c);
-int iscntrl(int c);
-int isdigit(int c);
-int isgraph(int c);
-int islower(int c);
-int isprint(int c);
-int ispunct(int c);
-int isspace(int c);
-int isupper(int c);
-int isxdigit(int c);
-int tolower(int c);
-int toupper(int c);
+pure int isalnum(int c);
+pure int isalpha(int c);
+pure int isblank(int c);
+pure int iscntrl(int c);
+pure int isdigit(int c);
+pure int isgraph(int c);
+pure int islower(int c);
+pure int isprint(int c);
+pure int ispunct(int c);
+pure int isspace(int c);
+pure int isupper(int c);
+pure int isxdigit(int c);
+pure int tolower(int c);
+pure int toupper(int c);

src/core/stdc/wctype.d

@@ -23,22 +23,22 @@ nothrow:
 alias wchar_t wctrans_t;
 alias wchar_t wctype_t;
 
-int iswalnum(wint_t wc);
-int iswalpha(wint_t wc);
-int iswblank(wint_t wc);
-int iswcntrl(wint_t wc);
-int iswdigit(wint_t wc);
-int iswgraph(wint_t wc);
-int iswlower(wint_t wc);
-int iswprint(wint_t wc);
-int iswpunct(wint_t wc);
-int iswspace(wint_t wc);
-int iswupper(wint_t wc);
-int iswxdigit(wint_t wc);
+pure int iswalnum(wint_t wc);
+pure int iswalpha(wint_t wc);
+pure int iswblank(wint_t wc);
+pure int iswcntrl(wint_t wc);
+pure int iswdigit(wint_t wc);
+pure int iswgraph(wint_t wc);
+pure int iswlower(wint_t wc);
+pure int iswprint(wint_t wc);
+pure int iswpunct(wint_t wc);
+pure int iswspace(wint_t wc);
+pure int iswupper(wint_t wc);
+pure int iswxdigit(wint_t wc);
 
 int       iswctype(wint_t wc, wctype_t desc);
 @system wctype_t  wctype(in char* property);
-wint_t    towlower(wint_t wc);
-wint_t    towupper(wint_t wc);
+pure wint_t    towlower(wint_t wc);
+pure wint_t    towupper(wint_t wc);
 wint_t    towctrans(wint_t wc, wctrans_t desc);
 @system wctrans_t wctrans(in char* property);