Check uint16_t and uint8_t support correctly

Fixes #177.
Merge branch '2.6'
Add JSON_REAL_PRECISION

Fixes #178.
Enable usage of AddressSanitizer to check Jansson
Remove unneeded undef
Merge pull request #180 from Sannis/master

Enable usage of AddressSanitizer to check Jansson
Merge remote-tracking branch 'upstream/master'