Remove C_TIME_FUZZY_DATES, C_TIME_DATETIME_ONLY, C_TIME_TIME_ONLY

Under terms of this task we'll do the following things:

• Remove completely C_TIME_DATETIME_ONLY
• Remove C_TIME_FUZZY_DATES, but keep TIME_FUZZY_DATES
• Remove C_TIME_TIME_ONLY, but keep TIME_TIME_ONLY

Rationale:

• C_TIME_FUZZY_DATES is not needed: TIME_FUZZY_DATES is used in /sql only
• C_TIME_DATETIME_ONLY is used internally in functions defined in my_time.cc an is never passed outside
• C_TIME_TIME_ONLY is confusing, see below.

Functions in sql-common/my_time.c have confusing names and work inconsistently to each other:

• str_to_datetime() returns TIME if TIME_TIME_ONLY is set, or DATETIME or DATE otherwise
• number_to_datetime() returns DATETIME or DATE (and never TIME)
• str_to_time() returns DATETIME, DATE or TIME, dependently on length and flags
• number_to_time() returns DATETIME, DATE or TIME, independently from flags

We'll replace them to self-descriptive functions, which won't depend on flags:

• str_to_datetime_or_date_or_time()
• str_to_datetime_or_date()
• number_to_datetime_or_date()
• number_to_time_only()

Instead of passing C_TIME_TIME_ONLY to functions from my_time.cc, the upper level will choose between the new functions.

This will help to add support of time intervals easier soon: the C++ level will have a new flag TIME_TIME_INTERVAL.