Document length limit of OS_MAX_PATH_LEN and OS_MAX_API_NAME includes null terminator

**Is your feature request related to a problem? Please describe.**
Documentation not clear

**Describe the solution you'd like**
Document length limit of OS_MAX_PATH_LEN and OS_MAX_API_NAME includes null terminator

**Describe alternatives you've considered**
None

**Additional context**
nasa/osal#88

**Requester Info**
Jacob Hageman - NASA/GSFC