[i18n] Initial i18n support.

- Add initial GetText .MO parser
- Add translation struct and helpers
- Pluralized lookup

 TODO:
- Support for more translation catalog file formats.

core/i18n/example/i18n_example.odin

@@ -0,0 +1,64 @@
+package i18n_example
+
+import "core:mem"
+import "core:fmt"
+import "core:i18n"
+
+LOC :: i18n.get
+
+_main :: proc() {
+	using fmt
+
+	err: i18n.Error
+
+	/*
+		Parse MO file and set it as the active translation so we can omit `get`'s "catalog" parameter.
+	*/
+	i18n.ACTIVE, err = i18n.parse_mo(#load("nl_NL.mo"))
+	defer i18n.destroy()
+
+	if err != .None { return }
+
+	/*
+		These are in the .MO catalog.
+	*/
+	println("-----")
+	println(LOC(""))
+	println("-----")
+	println(LOC("There are 69,105 leaves here."))
+	println("-----")
+	println(LOC("Hellope, World!"))
+
+	/*
+		For ease of use, pluralized lookup can use both singular and plural form as key for the same translation.
+	*/
+	println("-----")
+	printf(LOC("There is %d leaf.\n", 1), 1)
+	printf(LOC("There is %d leaf.\n", 42), 42)
+
+	printf(LOC("There are %d leaves.\n", 1), 1)
+	printf(LOC("There are %d leaves.\n", 42), 42)
+
+	/*
+		This isn't.
+	*/
+	println("-----")
+	println(LOC("Come visit us on Discord!"))
+}
+
+main :: proc() {
+	using fmt
+
+	track: mem.Tracking_Allocator
+	mem.tracking_allocator_init(&track, context.allocator)
+	context.allocator = mem.tracking_allocator(&track)
+
+	_main()
+
+	if len(track.allocation_map) > 0 {
+		println()
+		for _, v in track.allocation_map {
+			printf("%v Leaked %v bytes.\n", v.location, v.size)
+		}
+	}
+}

core/i18n/example/messages.pot

@@ -0,0 +1,30 @@
+# Odin i18n Example
+# Copyright (C) 2021 Jeroen van Rijn
+# This file is distributed under the same license as the PACKAGE package.
+# Jeroen van Rijn <Kelimion@users.noreply.github.com>, 2021.
+#
+#, fuzzy
+msgid   ""
+msgstr  "Project-Id-Version: Example 0.0.1\n"
+        "Report-Msgid-Bugs-To: Jeroen van Rijn <Kelimion@users.noreply.github.com>\n"
+        "POT-Creation-Date: 2021-11-27 19:23+0100\n"
+        "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
+        "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+        "Language: en-GB\n"
+        "MIME-Version: 1.0\n"
+        "Content-Type: text/plain; charset=UTF-8\n"
+        "Content-Transfer-Encoding: 8bit\n"
+
+#: i18n_example.odin:28
+msgid "There are 69,105 leaves here."
+msgstr "Er zijn hier 69.105 bladeren."
+
+#: i18n_example.odin:30
+msgid "Hellope, World!"
+msgstr "Hallo, Wereld!"
+
+#: i18n_example.odin:36
+msgid "There is %d leaf.\n"
+msgid_plural "There are %d leaves.\n"
+msgstr[0] "Er is %d blad.\n"
+msgstr[1] "Er zijn %d bladeren.\n"

core/i18n/example/nl_NL.po

@@ -0,0 +1,33 @@
+# Odin i18n Example
+# Copyright (C) 2021 Jeroen van Rijn
+# This file is distributed under the same license as the PACKAGE package.
+# Jeroen van Rijn <Kelimion@users.noreply.github.com>, 2021.
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: Example 0.0.1\n"
+"Report-Msgid-Bugs-To: Jeroen van Rijn <Kelimion@users.noreply.github.com>\n"
+"POT-Creation-Date: 2021-11-27 19:23+0100\n"
+"PO-Revision-Date: 2021-11-28 02:56+0100\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+"Language-Team: Odin Language Team\n"
+"X-Generator: Poedit 3.0\n"
+"Last-Translator: Jeroen van Rijn\n"
+"Plural-Forms: nplurals=2; plural=(n != 1);\n"
+"Language: nl_NL\n"
+
+#: i18n_example.odin:28
+msgid "There are 69,105 leaves here."
+msgstr "Er zijn hier 69.105 bladeren."
+
+#: i18n_example.odin:30
+msgid "Hellope, World!"
+msgstr "Hallo, Wereld!"
+
+#: i18n_example.odin:36
+msgid "There is %d leaf.\n"
+msgid_plural "There are %d leaves.\n"
+msgstr[0] "Er is %d blad.\n"
+msgstr[1] "Er zijn %d bladeren.\n"