Makefile: Refactor -package-id and macro flags to HFLAGS

All places HFLAGS is used also included these flags, and they make
sense for all GHC invocations in our build.
Makefile: Remove spurious HS_REGEX_PCRE flags

They were removed from configure.ac and replaced by the MIN_VERSION_*
flags which are now passed by default via HFLAGS.