Fix even more Clang warnings.

This patch disables shift-sign-overflow warnings for now. It also
fixes most -Wfloat-equal warnings and -Wextra-semi warnings.

llvm-svn: 343438
diff --git a/libcxx/include/regex b/libcxx/include/regex
index db15f78..1858500 100644
--- a/libcxx/include/regex
+++ b/libcxx/include/regex
@@ -1352,9 +1352,9 @@
     virtual ~__node() {}
 
     _LIBCPP_INLINE_VISIBILITY
-    virtual void __exec(__state&) const {};
+    virtual void __exec(__state&) const {}
     _LIBCPP_INLINE_VISIBILITY
-    virtual void __exec_split(bool, __state&) const {};
+    virtual void __exec_split(bool, __state&) const {}
 };
 
 // __end_state