Build on AIX fails because "opj_includes.h" is included after system headers

[smuehlst]

This is a follow-up to issue #620. The fix for the restrict pointers lets the build progress further, but the build now fails on a subsequent file:

[ 25%] Building C object src/lib/openjp2/CMakeFiles/openjp2.dir/opj_clock.c.o
"/usr/include/stdio.h", line 498.12: 1506-343 (S) Redeclaration of fgetpos64 differs from previous declaration on line 297 of "/usr/include/stdio.h".
"/usr/include/stdio.h", line 498.12: 1506-377 (I) The type "long long*" of parameter 2 differs from the previous type "long* restrict".
"/usr/include/stdio.h", line 501.12: 1506-343 (S) Redeclaration of fseeko64 differs from previous declaration on line 441 of "/usr/include/stdio.h".
"/usr/include/stdio.h", line 501.12: 1506-377 (I) The type "long long" of parameter 2 differs from the previous type "long".
"/usr/include/stdio.h", line 502.12: 1506-343 (S) Redeclaration of fsetpos64 differs from previous declaration on line 299 of "/usr/include/stdio.h".
"/usr/include/stdio.h", line 502.12: 1506-377 (I) The type "const long long*" of parameter 2 differs from the previous type "const long*".
"/usr/include/stdio.h", line 503.16: 1506-343 (S) Redeclaration of ftello64 differs from previous declaration on line 442 of "/usr/include/stdio.h".
"/usr/include/stdio.h", line 503.16: 1506-050 (I) Return type "long long" in redeclaration is not compatible with the previous return type "long".
"/home/stm/src/openjpeg_aix/src/lib/openjp2/openjpeg.h", line 75.9: 1506-224 (I) Incorrect pragma ignored.

I tracked this down to the fact the "opj_includes.h" is included after system headers in opj_clock.c:

#ifdef _WIN32
#include <windows.h>
#else
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/times.h>
#endif /* _WIN32 */
#include "opj_includes.h"

Inside "opj_includes.h" "opj_config_private.h" is included, and the comment says that is must be included before any system headers:

/*
 * This must be included before any system headers,
 * since they can react to macro defined there
 */
#include "opj_config_private.h"

This requirement is violated by including "opj_includes.h" after system headers in opj_clock.c. If I move the "opj_includes" to the top in opj_clock.c, it compiles successfully.

[smuehlst]

Created pull request #634-