Provide Snap package for Linux (#468)

Add support for building binary snap packages with snapcraft.

Snaps are containerised software packages that are simple to create and
install. They auto-update and are safe to run. And because they bundle
their dependencies, they work on all major Linux systems without modif-
ication.  -- from Snapcraft website

Refer-to: Snapcraft - Snaps are universal Linux packages
          <https://snapcraft.io/>

Signed-off-by: 林博仁(Buo-ren Lin) <Buo.Ren.Lin@gmail.com>

.gitignore

@@ -56,3 +56,10 @@ xcuserdata
 
 /packages/
 /win32/distrib-*
+
+/*.snap
+/poedit_source.tar.bz2
+/parts/
+/prime/
+/stage/
+/snap/.snapcraft/

snap/.editorconfig

@@ -0,0 +1,11 @@
+# EditorConfig for Snap Packaging
+# http://EditorConfig.org
+
+## This config only applies to this folder
+root = true
+
+[*.{yaml,yamllint}]
+indent_style = space
+indent_size = 2
+insert_final_newline = true
+trim_trailing_whitespace = true

snap/.yamllint

@@ -0,0 +1,17 @@
+# yamllint Configuration File for Snappy Packaging
+# https://yamllint.readthedocs.io
+#
+
+extends: default
+
+rules:
+  comments:
+    # Comments without starting space is disabled code
+    require-starting-space: false
+    min-spaces-from-content: 1
+  comments-indentation: disable
+  document-start: disable
+  line-length:
+    # /parts/*/source key's value is URL
+    allow-non-breakable-inline-mappings: true
+    max: 100

snap/README

@@ -0,0 +1,5 @@
+
+  Introduction
+================
+
+This is the snap package definition to build a snap package of Poedit

snap/patches/enchant-fix-build.patch

@@ -0,0 +1,11 @@
+--- src/Makefile.am	2017-04-05 05:13:57.000000000 +0800
++++ src/Makefile.am	2018-05-30 23:37:16.035641307 +0800
+@@ -6,6 +6,8 @@
+
+ libenchant_la_LIBADD= $(ENCHANT_LIBS) @ENCHANT_WIN32_RESOURCE@
+
++libenchant_la_LIBTOOLFLAGS = --tag=CC
++
+ libenchant_la_LDFLAGS = -no-undefined -export-symbols-regex '^enchant_.*'
+ if OS_WIN32
+ libenchant_la_LDFLAGS += -avoid-version

snap/patches/postprocess-desktop-entries.sed

@@ -0,0 +1,28 @@
+# This sed script processes desktop entries of the snapped
+# application.
+#
+# Documentation:
+#
+# * GNU Sed Manual
+#   https://www.gnu.org/software/sed/manual
+#     * `sed` script overview - `sed` scripts
+#     * `sed` commands summary - `sed` scripts
+#     * The `s` Command - `sed` scripts
+#     * Overview of basic regular expression syntax - Regular
+#       Expressions: selecting text
+#     * Back-references and Subexpressions - Regular Expressions:
+#       selecting text
+
+## Append '(Snappy Edition)' to the application name to make it
+## distinguishable with the other same application using different
+## software distribution technologies
+##
+## FIXME: The appended string is not localizable, the proper way to
+##        implement this is to probably use a new X-Snappy-Name keys
+##        with localestring format to let the translators fill in
+##        additional localized string and use these values to replace
+##        the Name keys here.
+s/^\(Name\(\[.\+\]\)\?=.*\)$/\1 (Snappy Edition)/g
+
+## Fix-up application icon lookup
+s|^Icon=.*|Icon=\${SNAP}/meta/gui/icon.png|