Added option for people to use an existing PCRE build and updated .def generation for x64 systems (some symbols are set to be excluded from Win64 builds)
Also fixed the filter "PCRE" for the bundled PCRE as file layout changed
Don't keep the lists of source files for libglib, libgobject and
libgio in the VS project files in addition to the canonical location,
the corresponding Makefile.am files.
Instead, generate the corresponding .vcproj files at make dist time
using the C preprocessor, from template files called .vcprojin. We
still list explicitly in the .vcprojin files some of the
Windows-specific source files, and the sources files of gnulib and
pcre.