WIP: Moved sources int src/, separated most of the source code from Perl.

The XS was left only for the unit / integration tests, and it links
libslic3r only. No wxWidgets are allowed to be used from Perl starting
from now.

src/png/zlib/zlib.pc.in

@@ -0,0 +1,13 @@
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+sharedlibdir=@sharedlibdir@
+includedir=@includedir@
+
+Name: zlib
+Description: zlib compression library
+Version: @VERSION@
+
+Requires:
+Libs: -L${libdir} -L${sharedlibdir} -lz
+Cflags: -I${includedir}