[pdf-devel] make syntax-check

[jemarch]

Hi hackers.

I have been imported the maintainer-makefile module from gnulib in the
libgnupdf source tree.

That module provides some more make targets, useful for the
maintainership of the package.

One of the new targets is 'syntax-check'. It performs a check of
common pitfalls on the source code and GCS conformance. 

Please do a make syntax-check before to send a patch.

Thanks.