libraw: fix build with old glibc versions

Prior to glibc 2.18, definitions like SIZE_MAX or INT_FAST32_MAX from
<stdint.h> were only made available for C code, or in C++ if
__STDC_LIMIT_MACROS was defined.

The code from jasper uses such definitions, without defining
__STDC_LIMIT_MACROS. Unfortunately, defining __STDC_LIMIT_MACROS in
the jasper headers doesn't work, since <stdint.h> has already been
included before, at a point where __STDC_LIMIT_MACROS was not defined.

So to solve this problem, we simply pass -D__STDC_LIMIT_MACROS in
CXXFLAGS when building libraw with jasper support.

Fixes:

  http://autobuild.buildroot.net/results/908aef6c82d56060933713df217b6b2ba21a01b0/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>