Since started, the VAX backend doesn't compile with config-list.mk

Since started, the VAX backend doesn't compile with config-list.mk
because one of VAX's macros doesn't use its argument:

g++ -c   -g -O2 -DIN_GCC  -DCROSS_DIRECTORY_STRUCTURE  -fno-exceptions -fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual -Wmissing-format-attribute -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Werror -fno-common  -DHAVE_CONFIG_H -I. -I. -I../../../gcc/gcc -I../../../gcc/gcc/. -I../../../gcc/gcc/../include -I../../../gcc/gcc/../libcpp/include -I/opt/cfarm/mpc/include  -I../../../gcc/gcc/../libdecnumber -I../../../gcc/gcc/../libdecnumber/dpd -I../libdecnumber -I../../../gcc/gcc/../libbacktrace    -o loop-invariant.o -MT loop-invariant.o -MMD -MP -MF ./.deps/loop-invariant.TPo ../../../gcc/gcc/loop-invariant.c
../../../gcc/gcc/loop-invariant.c: In function ‘bool check_dependency(basic_block, df_ref, bitmap)’:
../../../gcc/gcc/loop-invariant.c:789:20: error: unused variable ‘regno’ [-Werror=unused-variable]
       unsigned int regno = DF_REF_REGNO (use);
                    ^
cc1plus: all warnings being treated as errors
make[2]: *** [loop-invariant.o] Error 1

This should fix it:

2014-01-15  Jan-Benedict Glaw  <jbglaw@lug-owl.de>

	* config/vax/vax.h (FUNCTION_ARG_REGNO_P): Fix unused variable warning.

[BR]: http://gcc.gnu.org/ml/gcc-patches/2014-01/msg00882.html

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@206775 138bc75d-0d04-0410-961f-82ee72b054a4