Fix syntax in 3.8.0-2017-07-28.sql

[wojsmol]

#Pull Request for Issue # .

Summary of Changes

Fixed syntax in 3.8.0-2017-07-28.sql update files for mysql and postgresql to be detected by Joomla schema checker on update.

Testing Instructions

1. Install latest staging on mysql or postgresql
2. Go to database fixer and remember number of checked database changes.(in my case 146)
3. Apply PR.
4. Go to database fixer and check number of checked database changes should be one more then in point 2 (in my case 147).
   or code review

Expected result

147 database changes were checked.

Actual result

146 database changes were checked.

Documentation Changes Required

N/A

cc @alikon @csthomas @twister65 for postgresql testing

[twister65]

ADD COLUMN is only for postgreSQL:
ALTER TABLE "#__fields_groups" ADD COLUMN "params" TEXT NOT NULL;

For mySQL, it's only ADD :
ALTER TABLE '#__fields_groups' ADD 'params' TEXT NOT NULL AFTER 'ordering';

[wojsmol]

@twister65 For MySQL ADD and ADD COLUMN are both valid but only ADD COLUMN is recognised by Joomla schema manager see

joomla-cms/libraries/src/Schema/ChangeItem/MysqlChangeItem.php

Lines 78 to 87 in 691e472

	if ($command === 'ALTER TABLE')
	{
	$alterCommand = strtoupper($wordArray[3] . ' ' . $wordArray[4]);
	if ($alterCommand === 'ADD COLUMN')
	{
	$result = 'SHOW COLUMNS IN ' . $wordArray[2] . ' WHERE field = ' . $this->fixQuote($wordArray[5]);
	$this->queryType = 'ADD_COLUMN';
	$this->msgElements = array($this->fixQuote($wordArray[2]), $this->fixQuote($wordArray[5]));
	}

[wojsmol]

pinging @mbabker