We can't pass Cygwin pathnames to non-Cygwin programs.

Tell file name and actual error in error message. Print error message
to stderr. Always exit with failure when not able to open an input or
output file.

This avoids warnings about linking both with normal and debugging
runtime. Matches more closely what the old build system does.

Plus various minor build tweaks.

ported a version of the patch at https://bugzilla.gnome.org/show_bug.cgi?id=656531 adjusted for libreoffice

centralise cut/paste coding designed to explicitly load i18n and
i18npool libraries if UNO is not bootstrapped. Instead fallback to
the process service manager, and require this to be initialized,
even for small tools.