Do not enforce the win32-msvc2010 platform.

Otherwise we cannot compile against msvc2013 or mingw.
Remove gif-writing support.
Properly pass MAKE_TOOL to preconfig.cmd on windows.
Make it possible to set the openssl libs on windows.

This can be done by setting the following environment variable in cmd:

set OPENSSL_LIBS=OPENSSL_LIBS=-lssleay32MT -llibeay32MT

Yes, the syntax is crude, but at least it works.
Only add qphantom plugin on non-windows platforms.
Enable pkgconfig on non-osx machines.

This is required to be able to compile PhantomJS
against other system libs by defining PKG_CONFIG_PATH.
Update Qt5 modules.