profiling.  Also,

Bug#26938: profiling client hang if used before enabled

In the SHOW command, not sending header data because we had no 
rows to send was a protocol violation.  Porting the SHOW PROFILE
command to use the Information Schema table avoids that problem.


mysql-test/r/profiling.result:
  Add headers of pre-profile SHOW test.
mysql-test/t/profiling.test:
  Verify that the protocol isn't violated if we ask for profiling 
  info before profiling has recorded anything.
sql/sql_parse.cc:
  Remove SQLCOM_SHOW_PROFILE and add a I_S schema table entry.
sql/sql_profile.cc:
  Add SHOW column-names and a new function that takes profile options
  set in the parser and packs a list of selected fields from the 
  I_S table implementation.
sql/sql_profile.h:
  Remove unused functions and add a new function.
sql/sql_show.cc:
  Add a pointer to the function that selects fields from I_S table
  for SHOW command.
sql/sql_yacc.yy:
  Prepare an I_S table for SHOW PROFILE.
sql/table.h:
  Rename to match the intention.