Merge pull request #35 from morevnaproject/master

Fixes for Linux and OSX build scripts. Also fixes plugins loading/
Win32 build: Provide detailed instructions about usage
Win32 build: Clarify build instructions even more
Win32 build: Fix SRCPREFIX detection
Win32 build: Don't try to install libxml++ debuginfo package if there's no such one.
Win32 build: Migrate to Mingw-w64 toolchain
Ensure binary_path is defined even if no NLS enabled
Win32 build: Force rebuild for boost and freetype
Win32 build: Fix toolchain host for mingw
Win64 build: Add support for Fedora's Mingw 64bit toolchain. Add support for debug builds.

* use ARCH=64 env variable to build synfig for Win64
* use DEBUG=1 to build in debug mode

Example:
$ ARCH=64 DEBUG=1 bash ./autobuild/fedora-crosscompile-win.sh
Fix 'loses precission' error when building for Win64
Win32 build: Don't install boost, since it built anyway
Fix "synfig studio is already running" error when executed in Wine
Various fixes for Win32 build scripts
Fix installer creation procedure for Fedora's CrossCompile environment. Add support for 64bit installer.
Win32 build: Rig Cygwin installation with the rpm tool to provide access to Fedora's cross-compile toolchain packages. WIP. Rpm tool works.
Win32 build: Finish Fedora-to-Cygwin infrastructure. Now Cygwin is able to install precompiled packages from Fedora's MinGW toolchain.
Win64 build: Fix nsis package name (exists only for mingw32)
Win32 build: Clean source tree when launched without any arguments (full rebuild)
Win32 build: Give a proper name to installer file