Merge pull request #465 from houqp/houqp-master

add language setting menu item
Fix dealing with filenames containing spaces

and missing GestureRange require
Merge pull request #467 from thotypous/master

Fix dealing with filenames containing spaces
Update koreader-base
Language chooser fixes

- Change order of module loading so that every string is localized
- Fix changing the language to English
Merge pull request #469 from thotypous/master

Update koreader-base and language chooser fixes
Fix crash trying to select text in an empty page
Merge pull request #470 from thotypous/fix-box-empty-page

Fix crash trying to select text in an empty page
calculate maximum global cache size from free RAM
In reflowing scroll mode with 2 pages hinting, 4 full page blitbuffers
and koptcontexts should stay well in cache in the most demanding cases,
with two pages shown on screen and two pages rendered in background.
Since blitbuffer size is halved the size of page, we need cache size
to be 6 times an average reflowed page size.

For Kobo Aura HD which has a resolution of 1440×1080, a reflowed page
could become 1080×4800. So 30MB of cache is demanded for this case.

This PR implements dynamic cache size allocating according to size of
system free memory. By default it will use 20 percent of free RAM with
a clip specified by DGLOBAL_CACHE_SIZE_MINIMUM and
DGLOBAL_CACHE_SIZE_MAXIMUM which are 10MB and 30MB respectively by default.
Merge pull request #472 from chrox/master

calculate maximum global cache size from free RAM
rename language_po setting entry to language
update po