Apply formatting/style tweaks to comply with compile time diagnostics for g++ and clang++ (#686)

* Add compilation flags: -Wshadow -Weffc++ -pedantic -pedantic-errors
* Delete implicit copy & move constructors & assignment operators
  in classes with pointer data members.
* An exception to the above: Add default copy & move constructors &
  assignment operators for the Binary class.
* Convert boolean RegEx operators to binary operators.
* Initialize all members in all classes in ctors.
* Let default ctor delegate to the converting ctor in
  Binary and RegEx
* Don't change any tests except regex_test (as a result of the change
  to binary operators).

Note: https://bugzilla.redhat.com/show_bug.cgi?id=1544675 makes
-Weffc++ report a false positive in "include/yaml-cpp/node/impl.h".

src/regex_yaml.h

@@ -31,14 +31,14 @@ enum REGEX_OP {
 class YAML_CPP_API RegEx {
  public:
   RegEx();
-  RegEx(char ch);
+  explicit RegEx(char ch);
   RegEx(char a, char z);
   RegEx(const std::string& str, REGEX_OP op = REGEX_SEQ);
   ~RegEx() {}
 
   friend YAML_CPP_API RegEx operator!(const RegEx& ex);
-  friend YAML_CPP_API RegEx operator||(const RegEx& ex1, const RegEx& ex2);
-  friend YAML_CPP_API RegEx operator&&(const RegEx& ex1, const RegEx& ex2);
+  friend YAML_CPP_API RegEx operator|(const RegEx& ex1, const RegEx& ex2);
+  friend YAML_CPP_API RegEx operator&(const RegEx& ex1, const RegEx& ex2);
   friend YAML_CPP_API RegEx operator+(const RegEx& ex1, const RegEx& ex2);
 
   bool Matches(char ch) const;
@@ -53,7 +53,7 @@ class YAML_CPP_API RegEx {
   int Match(const Source& source) const;
 
  private:
-  RegEx(REGEX_OP op);
+  explicit RegEx(REGEX_OP op);
 
   template <typename Source>
   bool IsValidSource(const Source& source) const;