RE: -Werror breaks autoconf tests, but not actual source code

[Millaway, John]

> > One of them is AC_HEADER_STDC, which gets a warning for 
> implicit declaration
> > of 'exit':
> 
> That problem is easily fixed as shown below.
> What other problems did you observe?

Thanks for the quick patch. Here are (portions of the log
for) three more troublesome tests:

(1)
configure:4874: checking whether yytext is a pointer
configure:4890: gcc -o conftest -Wall -g   conftest.c  -lfl >&5
lex.yy.c:949: warning: `yyunput' defined but not used

(2)
configure:7610: checking whether __func__ is declared
configure:7634: gcc -c -Wall -g  conftest.c >&5
conftest.c: In function `main':
conftest.c:70: warning: unused variable `p'

(3)
configure:5943: checking whether g++ accepts -g
configure:5964: g++ -c -g  conftest.cc >&5
configure:5970: $? = 0
configure:5974: test -z 
                         || test ! -s conftest.err
configure:5977: $? = 0
configure:5980: test -s conftest.o
configure:5983: $? = 0
configure:5994: result: yes
configure:6036: g++ -c -g -O2  conftest.cc >&5
configure:6042: $? = 0
configure:6046: test -z 
                         || test ! -s conftest.err
configure:6049: $? = 0
configure:6052: test -s conftest.o
configure:6055: $? = 0
configure:6081: g++ -c -g -O2  conftest.cc >&5
conftest.cc: In function `int main()':
conftest.cc:16: `exit' undeclared (first use this function)
conftest.cc:16: (Each undeclared identifier is reported only once for each 
   function it appears in.)
configure:6087: $? = 1
configure: failed program was: