Add support to build command line tools on MINGW.

Tested with msysgit 1.8.3 environment.
Make common wchar_t / utf-8 conversion functions for MSVC tools.
Tweaks to ink annotation for smoothness.

Patch from "andyhan2000" to make the ink annotations smoother.
Move header files into separate include directory.
Merge common and internal headers into one.
Fix win32 project files.
Split fitz.h into subheaders.
Add explicit #include for header file interdependencies.
Split pdf.h into subheaders.
Move fz_write_pixmap wrapper into pdfextract (its only user).
Fix makefile header dependencies.
Add gen_ prefix to generated header files.