Problem: Missing detection of standards greater than C++11

[gummif]

Solution: Add macros detecting C++14 and C++17

[coveralls]

Pull Request Test Coverage Report for Build 186

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 45.914%

---

Totals
Change from base Build 178:	0.1%
Covered Lines:	1944
Relevant Lines:	4234

---

💛 - Coveralls