Fix three problems with pcre for portability;

  1. study.c's pointer arg didn't jive with pcre_fullinfo()'s prototype,
     however there was no (trivial) way to get them to concur.  Cast in
     this case was the least of several evils.

  2. byteflip had an error for high-bit set bytes, because right shift
     signed is allowed to extend the sign bit.  These had to be unsigned,
     and the real_pcre types were the safest way to do this.

  3. split byteflip into byteflip2/4, to drop size truncation emits, 
     as the arguments are unambigiously 16 or 32 bits as defined 
     in pcre_internal.h.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@157948 13f79535-47bb-0310-9956-ffa450edef68