Implement FNM_CASEFOLD for the fnmatch function

[markdirish]

• Implement FNM_CASEFOLD to allow for case-insensitive matching with fnmatch
• Create a FNM_PATHNAME alias of FNM_FILE_NAME for GNU compatibility

[markdirish]

Created a test file to ensure that, when linking against libutil.so, programs can use FNM_CASEFOLD:

#include <fnmatch.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
  const char *pattern = "abcdefgh";
  const char *string  = "AbCdEfGh";

  int result = fnmatch(pattern, string, 0);

  printf("Result is: %d\nExpected value: %d\n", result, FNM_NOMATCH);

  result = fnmatch(pattern, string, FNM_CASEFOLD);

  printf("Result is: %d\nExpected value: %d\n", result, 0);

  return 0;
}

$ ./fnmatchtest 
Result is: 1
Expected value: 1
Result is: 0
Expected value: 0