lib/libedit/history.c broke the build

[Paul Goyette <paul%whooppee.com@localhost>]

#   compile  libedit/historyn.o
/test-bed/tools/bin/x86_64--netbsd-gcc -O2 -std=gnu99  -Wall 
-Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wno-sign-compare  
-Wno-traditional  -Wa,--fatal-warnings -Wreturn-type -Wswitch -Wshadow 
-Wcast-qual -Wwrite-strings -Wextra -Wno-unused-parameter -Wno-sign-compare 
-Wsign-compare  -Werror     -DWIDECHAR -I. -I/test-bed/src/lib/libedit -I. 
-I/test-bed/src/lib/libedit   --sysroot=/test-bed/dst  -c    historyn.c -o 
historyn.o
cc1: warnings being treated as errors
In file included from historyn.c:3:
/test-bed/src/lib/libedit/history.c: In function 'history_save':
/test-bed/src/lib/libedit/history.c:818: warning: assignment discards 
qualifiers from pointer target type

*** Failed target:  historyn.o


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