open-axiom: ftbfs with GCC-5

Imported from Debian bug http://bugs.debian.org/778041:

Package: src:open-axiom
Version: 1.5.0~svn3056+ds-1
Severity: normal
Tags: sid stretch
User: <email address hidden>
Usertags: ftbfs-gcc-5

Please keep this issue open in the bug tracker for the package it
was filed for. If a fix in another package is required, please
file a bug for the other package (or clone), and add a block in this
package. Please keep the issue open until the package can be built in
a follow-up test rebuild.

The package fails to build in a test rebuild on at least amd64 with
gcc-5/g++-5, but succeeds to build with gcc-4.9/g++-4.9. The
severity of this report may be raised before the stretch release.

The full build log can be found at:
http://people.debian.org/~doko/logs/gcc5-20150205/open-axiom_1.5.0~svn3056+ds-1_unstable_gcc5.log
The last lines of the build log are at the end of this report.

To build with GCC 5, either set CC=gcc-5 CXX=g++-5 explicitly,
or install the gcc, g++, gfortran, ... packages from experimental.

  apt-get -t experimental install g++

Common build failures are C11 as the default C mode, new warnings
resulting in build failures with -Werror turned on, or new/dropped
symbols in Debian symbols files. For other C/C++ related build failures
see the porting guide at http://gcc.gnu.org/gcc-5/porting_to.html

[...]
../../../src/hyper/ht_icon:22:50: error: narrowing conversion of '207' from 'int' to 'char' inside { }
../../../src/hyper/ht_icon:22:50: error: narrowing conversion of '128' from 'int' to 'char' inside { }
../../../src/hyper/ht_icon:22:50: error: narrowing conversion of '254' from 'int' to 'char' inside { }
../../../src/hyper/ht_icon:22:50: error: narrowing conversion of '128' from 'int' to 'char' inside { }
In file included from ../../../src/hyper/initx.c:73:0:
../../../src/hyper/mouse11.bitmap:8:50: error: narrowing conversion of '128' from 'int' to 'char' inside { }
    0xc0, 0x47, 0x00, 0x21, 0x80, 0x10, 0x00, 0x0f};
                                                  ^
../../../src/hyper/mouse11.bitmap:8:50: error: narrowing conversion of '192' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.bitmap:8:50: error: narrowing conversion of '144' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.bitmap:8:50: error: narrowing conversion of '192' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.bitmap:8:50: error: narrowing conversion of '128' from 'int' to 'char' inside { }
In file included from ../../../src/hyper/initx.c:74:0:
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '128' from 'int' to 'char' inside { }
    0xc0, 0x47, 0x00, 0x21, 0x80, 0x10, 0x00, 0x0f};
                                                  ^
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '192' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '192' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '224' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '224' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '240' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '240' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '248' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '240' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '224' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '192' from 'int' to 'char' inside { }
../../../src/hyper/mouse11.mask:6:50: error: narrowing conversion of '128' from 'int' to 'char' inside { }
../../../src/hyper/initx.c: In function 'void set_name_and_icon()':
../../../src/hyper/initx.c:386:17: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
     ch.res_name = "HyperDoc";
                 ^
../../../src/hyper/initx.c: At global scope:
../../../src/hyper/initx.c:596:53: error: narrowing conversion of '255' from 'int' to 'char' inside { }
                               0xff, 0xff, 0xff, 0xff};
                                                     ^
../../../src/hyper/initx.c:596:53: error: narrowing conversion of '255' from 'int' to 'char' inside { }
../../../src/hyper/initx.c:596:53: error: narrowing conversion of '255' from 'int' to 'char' inside { }
../../../src/hyper/initx.c:596:53: error: narrowing conversion of '255' from 'int' to 'char' inside { }
make[3]: *** [initx.o] Error 1
Makefile:404: recipe for target 'initx.o' failed
make[3]: Leaving directory '/«BUILDDIR»/open-axiom-1.5.0~svn3056+ds/build-tree/src/hyper'
make[2]: *** [all-hyper-pre] Error 2
Makefile:816: recipe for target 'all-hyper-pre' failed
make[2]: Leaving directory '/«BUILDDIR»/open-axiom-1.5.0~svn3056+ds/build-tree/src'
make[1]: *** [all-local] Error 2
Makefile:1008: recipe for target 'all-local' failed
make[1]: Leaving directory '/«BUILDDIR»/open-axiom-1.5.0~svn3056+ds/build-tree'
make: *** [build-stamp] Error 2
debian/rules:60: recipe for target 'build-stamp' failed
dpkg-buildpackage: error: debian/rules build-arch gave error exit status 2