Patch for bug #67839 (mysqli does not handle 4-byte floats correctly)

Before the patch, a value of 9.99 in a FLOAT column came out of mysqli
as 9.9998998641968. This is because it would naively cast a 4-byte float
into PHP's internal 8-byte double.
To fix this, with GCC we use the built-in decimal support to "up-convert"
the 4-byte float to a 8-byte double.
When that is not available, we fall back to converting the float
to a string and then converting the string to a double. This mimics
what MySQL does.
Fix failing tests
Merge branch 'pull-request/772' into PHP-5.4

* pull-request/772:
  Fix failing tests
  Patch for bug #67839 (mysqli does not handle 4-byte floats correctly)

Before the patch, a value of 9.99 in a FLOAT column came out of mysqli
as 9.9998998641968. This is because it would naively cast a 4-byte float
into PHP's internal 8-byte double.
To fix this, with GCC we use the built-in decimal support to "up-convert"
the 4-byte float to a 8-byte double.
When that is not available, we fall back to converting the float
to a string and then converting the string to a double. This mimics
what MySQL does.
Add NEWS
Merge branch 'PHP-5.4' into PHP-5.5

* PHP-5.4:
  Add NEWS
  Fix failing tests
  Patch for bug #67839 (mysqli does not handle 4-byte floats correctly)

Conflicts:
	ext/mysqli/tests/table.inc
Fix another failing test
Update NEWS
Merge branch 'PHP-5.5' into PHP-5.6

* PHP-5.5:
  Update NEWS
  Fix another failing test
  Add NEWS
  Fix failing tests
  Patch for bug #67839 (mysqli does not handle 4-byte floats correctly)

Conflicts:
	ext/mysqli/tests/mysqli_change_user.phpt
Update NEWS