Add implementation of text() module.
Add new libraries to the build and check scripts.
Add debian package dependencies.
Add libraries to qmake config.
Skip build in case the library is already installed.
Patch Qt when building on Mavericks/XCode 5.0.1.

This is a workaround for compilation problems in that
environment:

- Disable tiff plugin which fails with duplicate symbol
  errors when linking. This is available as configure option.

- Disable core-wlan which fails compilation with lots
  of errors. This needs to patch the qmake config file.
Add new libraries to MacOS X build script.

Also move some general stuff into a separate script so
it can be shared by the MacOS X and the Linux build.
Include common script for Linux builds.
Add first set of test cases for text().
Add test cases for text alignment and text direction.
Fix dependency build script on MacOS X.
Force pkg-config to look in the local library folder.

Setting both PKG_CONFIG_PATH and PKG_CONFIG_LIBDIR should
force pkg-config to ignore system installed libraries. We
only want it to find locally compiled dependencies if the
variable OPENSCAD_LIBRARIES is set.
Move main text test cases to the heavy set and introduce a simple test.
Change sed calls to work on both MacOS X and Linux.

The syntax for the -i parameter is not compatible, so just write the
modified file temporarily and move it in place after the sed call.
Show a warning message in case some compile variables are set.

Currently warning is shown for:
- CFLAGS
- CXXFLAGS
- LDFLAGS
Add libxml2 to dependency build script and configure fontconfig to use it.
Add libxml2 to MacOS X build.
Add dialog to show all registered fonts.
Add gtk-doc-tools providing gtkdocize (needed for building harfbuzz).
Fix compilation in MinGW environment.