2.1.0: getrusage misdeclared locally on non-linux architectures

[olebole]

This is a forward of Debian bug #830253:

Builds of casacore on kFreeBSD and the Hurd failed with errors along the lines of

  /usr/include/i386-kfreebsd-gnu/sys/resource.h:87:69: error: declaration of 'int getrusage(__rusage_who_t, rusage*) throw ()' has a different exception specifier
   extern int getrusage (__rusage_who_t __who, struct rusage *__usage) __THROW;
                                                                       ^
  In file included from /«PKGBUILDDIR»/casacore/casa/OS/MemoryTrace.h:32:0,
                   from /«PKGBUILDDIR»/casa/Containers/Block.cc:29:
  /«PKGBUILDDIR»/casacore/casa/OS/Timer.h:58:16: error: from previous declaration 'int getrusage(int, rusage*)'
   extern "C" int getrusage(int, struct rusage*);
                  ^
  casa/CMakeFiles/casa_casa.dir/build.make:701: recipe for target 'casa/CMakeFiles/casa_casa.dir/Containers/Block.cc.o' failed

To address this error, I would suggest editing lines 44 and 192 of casa/OS/Timer.h and lines 47, 78, 118, 148, 183, 223, 254, and 290 of casa/OS/Timer.cc to check __GLIBC__ either instead of or in addition to AIPS_LINUX. (An even better fix would be to have the build system check whether a prototype is available.) There may well be references to AIPS_LINUX in other files that could also stand to be generalized.