MdeModulePkg/Core: Merge memory map after filtering paging capability

MdeModulePkg/Core: Merge memory map after filtering paging capability

Once the paging capabilities were filtered out, there might be some adjacent entries
sharing the same capabilities. It's recommended to merge those entries for the OS
compatibility purpose.

This patch makes use of existing method MergeMemoryMap() to do it. This is done by
simply turning this method from static to extern, and call it after filter code.

This patch is related to an issue described at
   https://bugzilla.tianocore.org/show_bug.cgi?id=753

This patch is also passed test of booting follow OSs:
    Windows 10
    Windows Server 2016
    Fedora 26
    Fedora 25

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>