[tlbuild] memleak fix for synctex lib

[Peter Breitenlohner]

On Mon, 4 Aug 2014, Norbert Preining wrote:

> Sebastian (in Cc), who send the original patch for making synctex
> a separate lib, has found a memory leak in the synctex code,
> and also a patchIn hi sown words:
>> There seems to be a memory leak in the implementation of _synctex_open.
>> build_output points to a memory location acquired with malloc, but
>> build_output is never passed to free. The attached patch adds the
>> necessary calls to clean up the allocated memory.

Hi Norbert, Sebastian,

applied with a minor modification: we absolutely don't want declarations
after statements in C.

Regards
Peter