Reduce memory footprint when linking

Linking QtWebKit on Linux x64 with debug symbols can use up to 11Gbyte
of memory. This can make it impossible to link on many systems.

This patch forces GCC 4.8+ to fully use DWARF-4 debug-types sections
to eleminate duplicate symbols and makes earlier GCC versions STABS
which also uses much less memory.

Task-number: QTBUG-36131

Change-Id: Ib1ba3e073b5984ead3a0badb935e7b89c01b962b
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>
Merge remote-tracking branch 'origin/release' into stable

Change-Id: I82f158687d0b5da3e85c025d720111b6b1414010
Make sure the correct position for the plugin is used when showing

When the plugin was windowed then it was always being shown at 0x0 of
the containing window rather than the correct position of the plugin
inside the containing window. This enesures it is placed correctly in
that case.

Task-number: QTBUG-31730
             QTBUG-33053
             QTBUG-32546

Change-Id: I5ce0321924d288437d483002e9cb6dd1c98b6863
Reviewed-by: Michael Bruning <michael.bruning@digia.com>