[WIP] Rework libxml2, libxslt and lxml (update versions)

[opacam]

The lxml recipe depends on those two libraries, if we update lxml we must update the two libraries (libxml2 and libxslt). This rework takes care of that and also:

• replace double quotes to single quotes because I think that it's more readable
• fix imports
• shortened lines

Note: Successfully build for python3 and python2 (tested some days ago in a real python3's app but it would be great that someone could test it again)

[AndreMiras]

Looking overall good to me. Let's see if Travis is happy about it.
I disagree with this (minor) point however replace double quotes to single quotes because I think that it's more readable I think it's a matter of taste, unless there's a PEP8 rule for it. So in general I don't touch something like that

[opacam]

Yes, you are right @AndreMiras, it's a personal taste the quotes 😬 (I knew before hand that this will be problematic 😏...if you want I will change to double quotes no problem). Anyway, as far as I know, it is recommended to be consistent along all the project, and now we have mixed quotes and before the change I checked some of the core modules and it seemed to me that single quotes are predominant...but I cannot be sure about that...so...the said...just tell me and I will change it .

[AndreMiras]

minor: why the -r flags?

[AndreMiras]

I usually tend not to switch from one to the other as it adds noise to the diff and makes reviewing a more difficult. But I would not go as far as asking to revert 😄
It's bit annoying Travis didn't make it to the end again, because we cannot see if it compiled OK.
p4a is way too verbose to me and I think this is an issue we should tacle soon or later.

Anyway looking good overall, thanks!

Edit: oops I didn't squash 😬

[RobertFlatt]

I'm having trouble building libxml2 , there is no file libxml2.* in the APK
/build/other_builds/libxml2/armeabi-v7a__ndk_target_21/libxml2/libxml2.la is created, but
/build/other_builds/libxml2/armeabi-v7a__ndk_target_21/libxml2/libs/libxml2.a is not created

Re installed p4a from master today

Looking in recipes/libxml2/init.py it seems the .a is explicitly not created, then copied elsewhere!

Can you please help me see what I am missing?

            # Ensure we only build libxml2.la as if we do everything
            # we'll need the glob dependency which is a big headache
            shprint(sh.make, "libxml2.la", _env=env)

            shutil.copyfile('.libs/libxml2.a',join(self.ctx.libs_dir, 'libxml2.a'))

Using:
p4a apk requirements=libxml2,python3,kivy

.p4a:

--dist_name=tstlib
--private .
--package=com.example.tstlib
--name Tstlib
--arch=armeabi-v7a
--sdk_dir /home/bobf/androidtools/sdk
--ndk_dir /home/bobf/androidtools/android-ndk-r17c
--ndk_version 17c
--android_api 28
--ndk-api 21
--version 0.0.0

Log file:
log_libxml2.txt