Resolve warnings on Windows

Appease the compiler by resolving some of the reported warnings,
including:

- Control paths that don't return.

- Potentially uninitialized variables.

- Unused local variables.

- Unreachable code.

- Type safety.

- Synchronize declarations with definitions for functions.

lib/roken/base64.c

@@ -93,7 +93,7 @@ base64_encode(const void *data, int size, char **str)
     }
     *p = 0;
     *str = s;
-    return strlen(s);
+    return (int) strlen(s);
 }
 
 #define DECODE_ERROR 0xffffffff

lib/roken/concat.c

@@ -100,7 +100,7 @@ roken_vmconcat (char **s, size_t max_len, va_list args)
 ROKEN_LIB_FUNCTION size_t ROKEN_LIB_CALL
 roken_mconcat (char **s, size_t max_len, ...)
 {
-    int ret;
+    size_t ret;
     va_list args;
 
     va_start(args, max_len);

lib/roken/dirent.c

@@ -87,7 +87,7 @@ opendir(const char * filespec)
     }
 
     do {
-        long len = strlen(fd.name);
+        size_t len = strlen(fd.name);
         struct dirent * e;
 
         if (dp->n_entries == dp->nc_entries) {

lib/roken/simple_exec_w32.c

@@ -80,7 +80,6 @@ wait_for_process_timed(pid_t pid, time_t (*func)(void *),
     hProcess = OpenProcess(SYNCHRONIZE, FALSE, pid);
 
     if (hProcess == NULL) {
-	DWORD dw = GetLastError();
         return SE_E_WAITPIDFAILED;
     }
 

lib/roken/snprintf.c

@@ -498,7 +498,7 @@ xyzprintf (struct snprintf_state *state, const char *char_format, va_list ap)
 		break;
 	    }
 	    case 'p' : {
-		unsigned long arg = (unsigned long)va_arg(ap, void*);
+		u_longest arg = (u_longest)va_arg(ap, void*);
 
 		len += append_number (state, arg, 0x10, "0123456789ABCDEF",
 				      width, prec, flags, 0);

lib/roken/unvis.c

@@ -126,7 +126,7 @@ rk_unvis(char *cp, int c, int *astate, int flag)
 			*astate = S_OCTAL2;
 			return (0);
 		case 'M':
-			*cp = (char)0200;
+			*cp = (u_char)0200;
 			*astate = S_META;
 			return (0);
 		case '^':