please don't use #pragma GCC system_header

[Stephan Bergmann]

On 11/14/2013 11:25 AM, Michael Stahl wrote:
> ... because it not only disables warnings, it also prevents generating
> Makefile dependencies for the file, and that is what caused everybody's
> build to break after yesterday's ICU upgrade.

Is that only relevant in "our own" files, or also in header files from 
bundled external modules (where I rather liked the occasional trick of 
silencing warnings wholesale with a single "#pragma GCC system_header" 
patch)?

Stephan