Task #5540: Apparently, the compile option -D_GLIBCXX_DEBUG causes all kinds...

Task #5540: Apparently, the compile option -D_GLIBCXX_DEBUG causes all kinds of hard to track problems with third-party packages, causing random segmentation faults in, e.g., casacore and pqxx. So I reverted this change.

CMake/variants/GNU.cmake

@@ -21,7 +21,7 @@ set(GNU_C_FLAGS_DEBUG    "-g")
 set(GNU_C_FLAGS_OPT      "-g -O2")
 set(GNU_C_FLAGS_OPT3     "-g -O3")
 set(GNU_CXX_FLAGS        "-W -Wall -Woverloaded-virtual -Wno-unknown-pragmas")
-set(GNU_CXX_FLAGS_DEBUG  "-g -D_GLIBCXX_DEBUG")
+set(GNU_CXX_FLAGS_DEBUG  "-g")
 set(GNU_CXX_FLAGS_OPT    "-g -O2")
 set(GNU_CXX_FLAGS_OPT3   "-g -O3")
 set(GNU_EXE_LINKER_FLAGS)