it turns out the only places where we have compiler warnings of
-W-parentheses-equality is the source code generated by ANTLR. strictly
speaking, this is valid C++ code, just not quite readable from the
hygienic point of view. so let's enable this warning in the source tree,
but only disable it when compiling the sources generated by ANTLR.
please note, this warning option is supported by both GCC and Clang,
so no need to test if it is supported.
for a sample of the warnings, see:
```
/home/kefu/dev/scylladb/build/cmake/cql3/CqlLexer.cpp:21752:38: error: equality comparison with extraneous parentheses [-Werror,-Wparentheses-equality]
if ( (LA4_0 == '$'))
~~~~~~^~~~~~
/home/kefu/dev/scylladb/build/cmake/cql3/CqlLexer.cpp:21752:38: note: remove extraneous parentheses around the comparison to silence this warning
if ( (LA4_0 == '$'))
~ ^ ~
```
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
c76486c508