[entropy.spm] PortagePlugin: use /var/tmp/entropy as mkdtemp() dir in doebuild()

This avoids problems for users using tmpfs /tmp
[entropy*] create const_mkdtemp() as tempfile.mkdtemp() wrapper.

using /tmp as TMPDIR is a no go, since on modern systems, /tmp is on
tmpfs with a very limited amount of fs size assigned. Use /var/tmp/entropy
(or /var/tmp as fallback) instead.
[entropy.core.settings.base] add missing _() import
[Rigo] paths: call mkdtemp with dir=/var/tmp
[entropy*] create const_mkstemp() as tempfile.mkstemp() wrapper.

using /tmp as TMPDIR is a no go, since on modern systems, /tmp is on
tmpfs with a very limited amount of fs size assigned. Use /var/tmp/entropy
(or /var/tmp as fallback) instead.
[entropy.const] const_mkdtemp: call makedirs() only if dir=etpConst['entropyunpackdir']
Release Entropy 188
Tagging Entropy version 188
[eit] utils: if sha1 or sha256 hashes are not available, print N/A
[equo] utils: if sha1 or sha256 hashes are not available, print N/A
[entropy.server] RepositoryConfigParser: add write() method
[entropy.client] move the repository config file prefix string to RepositoryConfigParser
[entropy.client] RepositoryConfigParser: add enable, disable, add, remove methods