C standard

[Alex Merry]

Currently, KDECompilerSettings.cmake in ECM sets -std=iso9899:1990 for C
code (C90).  Question: do we want to change this to -std=c99?

Bear in mind that our minimum GCC version (4.2) does not completely
support this standard.  In particular, the semantics for inline
functions don't match C99's until GCC 4.3, and there are some corner
cases for variable length arrays and complex numbers that are not fixed
until GCC 4.5.

Obviously, this won't affect that much code, since most of it is C++
(for which, incidentally, we set -std=c++0x, ie: C++11).

Alex