Disable use of gcc poison pragmas

Needs a rethink to avoid use of poisoned macros in system headers.
I see this on Ubuntu 16.04:

gcc -DHAVE_CONFIG_H   -I../Source/Include -I../Source/CParse
-I../Source/Include -I../Source/DOH -I../Source/CParse
-I../Source/Doxygen -I../Source/Preprocessor -I../Source/Swig
-I../Source/Modules   -g -O2 -Wall -W -pedantic -MT DOH/base.o -MD -MP
-MF $depbase.Tpo -c -o DOH/base.o DOH/base.c &&\
mv -f $depbase.Tpo $depbase.Po
In file included from /usr/include/string.h:630:0,
                 from DOH/dohint.h:21,
                 from DOH/base.c:15:
/usr/include/x86_64-linux-gnu/bits/string2.h:1282:19: error: attempt to
use poisoned "calloc"
        ? (char *) calloc ((size_t) 1, (size_t) 1)        \
                   ^
/usr/include/x86_64-linux-gnu/bits/string2.h:1284:32: error: attempt to
use poisoned "malloc"
      char *__retval = (char *) malloc (__len);       \
                                ^
/usr/include/x86_64-linux-gnu/bits/string2.h:1302:19: error: attempt to
use poisoned "calloc"
        ? (char *) calloc ((size_t) 1, (size_t) 1)        \
                   ^
/usr/include/x86_64-linux-gnu/bits/string2.h:1308:26: error: attempt to
use poisoned "malloc"
      __retval = (char *) malloc (__len);        \
                          ^

Source/DOH/doh.h

@@ -496,11 +496,15 @@ extern void DohMemoryDebug(void);
 /* This works around bison's template checking if malloc and free are defined,
  * which triggers GCC's poison checks.
  */
+/*
 #  pragma GCC poison malloc free
 # pragma GCC poison realloc calloc
+*/
 # endif
 /* Use Exit() instead (which will remove output files on error). */
+/*
 # pragma GCC poison abort exit
+*/
 #endif
 
 #endif				/* DOH_H */