Fix implicit conversion warnings in _XlcCreateDefaultCharSet

lcCharSet.c:187:50: warning: implicit conversion changes signedness:
      'int' to 'unsigned long' [-Wsign-conversion]
    tmp = Xmalloc(name_len + 1 + ct_sequence_len + 1);
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../../include/X11/Xlibint.h:453:32: note: expanded from macro 'Xmalloc'
                       ~~~~~~  ^~~~
lcCharSet.c:192:31: warning: implicit conversion changes signedness:
      'int' to 'unsigned long' [-Wsign-conversion]
    memcpy(tmp, name, name_len+1);
    ~~~~~~            ~~~~~~~~^~
lcCharSet.c:216:45: warning: implicit conversion changes signedness:
      'int' to 'unsigned long' [-Wsign-conversion]
    memcpy(tmp, ct_sequence, ct_sequence_len+1);
    ~~~~~~                   ~~~~~~~~~~~~~~~^~
lcCharSet.c:183:16: warning: implicit conversion loses integer precision:
      'unsigned long' to 'int' [-Wshorten-64-to-32]
    name_len = strlen(name);
             ~ ^~~~~~~~~~~~
lcCharSet.c:184:23: warning: implicit conversion loses integer precision:
      'unsigned long' to 'int' [-Wshorten-64-to-32]
    ct_sequence_len = strlen(ct_sequence);
                    ~ ^~~~~~~~~~~~~~~~~~~
lcCharSet.c:198:37: warning: implicit conversion loses integer precision:
     'long' to 'unsigned int' [-Wshorten-64-to-32]
        unsigned int length = colon - charset->name;
                     ~~~~~~   ~~~~~~^~~~~~~~~~~~~~~

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>