Update libzip and zlib submodules (#115)

Context: https://libzip.org/news/release-1.9.0.html
Context: https://libzip.org/news/release-1.9.1.html
Context: https://libzip.org/news/release-1.9.2.html
Context: https://zlib.net/ChangeLog.txt

`libzip` updated to v1.9.2, changes:

   * Add zip_file_is_seekable().
   * Improve compatibility with WinAES.
   * Fix encoding handling in zip_name_locate().
   * Add option to zipcmp to output summary of changes.
   * Various bug fixes and documentation improvements.

`zlib` updated to v1.2.12, changes:

   * Fix a deflate bug when using the Z_FIXED strategy that can result
     in out-of-bound accesses.
   * Fix a deflate bug when the window is full in deflate_stored().
   * Speed up CRC-32 computations by a factor of 1.5 to 3.
   * Use the hardware CRC-32 instruction on ARMv8 processors.
   * Speed up crc32_combine() with powers of x tables.
   * Add crc32_combine_gen() and crc32_combine_op() for fast combines

.gitmodules

@@ -10,7 +10,7 @@
 	branch = develop
 [submodule "external/bzip2"]
 	path = external/bzip2
-	url = git://sourceware.org/git/bzip2.git
+	url = https://sourceware.org/git/bzip2.git
 	branch = master
 [submodule "external/xz"]
 	path = external/xz

LibZipSharp.props

@@ -1,6 +1,6 @@
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
-    <_LibZipSharpAssemblyVersion>2.0.5</_LibZipSharpAssemblyVersion>
+    <_LibZipSharpAssemblyVersion>2.0.6</_LibZipSharpAssemblyVersion>
     <!--
       Nuget Version. You can append things like -alpha-1 etc to this value.
       But always leave the $(_LibZipSharpAssemblyVersion) value at the start.