While doc file make use of update-alternatives to fix confliction,
we should reconfigure update-alternatives for doc compression.

Such as util-linux-doc:
...
update-alternatives --install /usr/share/man/man1/last.1 last.1
  /usr/share/man/man1/last.1.util-linux 100
...
was updated by doc_compress to
...
update-alternatives --install /usr/share/man/man1/last.1.bz2 last.1.bz2
  /usr/share/man/man1/last.1.util-linux.bz2 100
...

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>

The previous detection missing the following manual file:
...
gawk-doc/usr/share/man/man3/readfile.3am
libpcap-doc/usr/share/man/man3/pcap_dump_open.3pcap
...

We use re to imporve it.

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>

A distribution compression policy should be established, and used by all
packages. It compressed man pages in ${mandir} and info pages in ${infodir}

1. The doc will be compressed to gz format by default, which is configured
in ${DOC_COMPRESS}

2. It will automatically correct the compressed doc which is not
in ${DOC_COMPRESS} but in ${DOC_COMPRESS_LIST} to the format
of ${DOC_COMPRESS} policy

3. It is easy to add a new type compression by editing
local.conf, such as:
...
DOC_COMPRESS_LIST_append = ' abc'
DOC_COMPRESS = 'abc'
DOC_COMPRESS_CMD[abc] = 'abc compress cmd ***'
DOC_DECOMPRESS_CMD[abc] = 'abc decompress cmd ***'
...

[YOCTO #1238]

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>