add toupper/tolower functions (for JuliaLang/julia#11471)

test/case.c

@@ -0,0 +1,50 @@
+#include "tests.h"
+#include <wctype.h>
+
+int main(int argc, char **argv)
+{
+     int error = 0, better = 0;
+     utf8proc_int32_t c;
+
+     (void) argc; /* unused */
+     (void) argv; /* unused */
+
+     /* some simple sanity tests of the character widths */
+     for (c = 0; c <= 0x110000; ++c) {
+          utf8proc_int32_t l = utf8proc_tolower(c);
+          utf8proc_int32_t u = utf8proc_toupper(c);
+
+          check(l == c || utf8proc_codepoint_valid(l), "invalid tolower");
+          check(u == c || utf8proc_codepoint_valid(u), "invalid toupper");
+
+          if (sizeof(wint_t) > 2 || c < (1<<16)) {
+               wint_t l0 = towlower(c), u0 = towupper(c);
+               
+               /* OS unicode tables may be out of date.  But if they
+                  do have a lower/uppercase mapping, hopefully it
+                  is correct? */
+               if (l0 != c && l0 != l) {
+                    fprintf(stderr, "MISMATCH %x != towlower(%x) == %x\n",
+                            l, c, l0);
+                    ++error;
+               }
+               else if (l0 != l) { /* often true for out-of-date OS unicode */
+                    ++better;
+                    /* printf("%x != towlower(%x) == %x\n", l, c, l0); */
+               }
+               if (u0 != c && u0 != u) {
+                    fprintf(stderr, "MISMATCH %x != towupper(%x) == %x\n",
+                            u, c, u0);
+                    ++error;
+               }
+               else if (u0 != u) { /* often true for out-of-date OS unicode */
+                    ++better;
+                    /* printf("%x != towupper(%x) == %x\n", u, c, u0); */
+               }
+          }
+     }
+     check(!error, "utf8proc case conversion FAILED %d tests.", error);
+     printf("More up-to-date than OS unicode tables for %d tests.\n", better);
+     printf("utf8proc case conversion tests SUCCEEDED.\n");
+     return 0;
+}