prepare multi-byte support

and fix isalpha crashes on bad libc's. Fixes GH #70.
e.g. UTF-8.

re.c

@@ -296,15 +296,15 @@ void re_print(regex_t* pattern)
 /* Private functions: */
 static int matchdigit(char c)
 {
-  return isdigit(c);
+  return isdigit((unsigned char)c);
 }
 static int matchalpha(char c)
 {
-  return isalpha(c);
+  return isalpha((unsigned char)c);
 }
 static int matchwhitespace(char c)
 {
-  return isspace(c);
+  return isspace((unsigned char)c);
 }
 static int matchalphanum(char c)
 {
@@ -407,6 +407,7 @@ static int matchstar(regex_t p, regex_t* pattern, const char* text, int* matchle
 {
   int prelen = *matchlength;
   const char* prepoint = text;
+  // TODO check if multibyte, and use mbtowc() then
   while ((text[0] != '\0') && matchone(p, *text))
   {
     text++;

tests/test1.c

@@ -4,6 +4,7 @@
 
 #include <stdio.h>
 #include <string.h>
+//#include <locale.h>
 #include "re.h"
 
 
@@ -90,6 +91,8 @@ char* test_vector[][4] =
   { NOK, "a\\",                       "a\\",              (char*) 0      },
   { NOK, "\\",                        "\\",               (char*) 0      },
   { OK,  "\\\\",                      "\\",               (char*) 1      },
+  // no multibyte support yet
+  //{ OK,  "\\w+",                      "Çüéâ",             (char*) 4      },
 };
 
 
@@ -106,6 +109,8 @@ int main()
     size_t nfailed = 0;
     size_t i;
 
+    //setlocale(LC_CTYPE, "en_US.UTF-8");
+
     for (i = 0; i < ntests; ++i)
     {
         pattern = test_vector[i][1];