classes/compress_doc.bbclass: compress man/info pages

classes/compress_doc.bbclass: compress man/info pages

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]

(From OE-Core rev: 5c833e188bbf25c35c24f78eaa761a191d6b5801)

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