QItemSelectionModel: avoid 24 relocations

Use qOffsetStringArray() instead of an array of pairs of pointers.

This unearthed a problem with SIGNAL and SLOT calling qFlagLocation()
(meaning in debug mode, the array was runtime-initialized, not just
relocated), which we work around by using the new QT_STRINGIFY_
{SIGNAL,SLOT} macros now.

Saves 24 relocations, but, interestingly, saves only 4b in text size
on GCC 11.2 Linux AMD64 -O2 C++20 builds (TEXT and DATA combined)
while saving 760b on the equivalent Clang 10 libc++ build (expected,
in both cases: 24 * (sizeof(void*) - sizeof(quint16))):

Clang:

  $ size qtbase/lib/libQt6Core.so.6.4.0
     text    data     bss     dec     hex filename
  5476156   90520   16185 5582861  55300d qtbase/lib/libQt6Core.so.6.4.0
  $ ~/bin/relinfo.pl qtbase/lib/libQt6Core.so.6.4.0
  qtbase/lib/libQt6Core.so.6.4.0: 6528 relocations, 3598 relative (55%), 2540 PLT entries, 2227 for local syms (87%), 0 users
  $ ninja libQt6Core.so
  [6/6] Creating library symlink qtbase/lib/libQt6Core.so.6 qtbase/lib/libQt6Core.so
  $ size qtbase/lib/libQt6Core.so.6.4.0
     text    data     bss     dec     hex filename
  5475604   90312   16185 5582101  552d15 qtbase/lib/libQt6Core.so.6.4.0
  $ ~/bin/relinfo.pl qtbase/lib/libQt6Core.so.6.4.0
  qtbase/lib/libQt6Core.so.6.4.0: 6504 relocations, 3574 relative (54%), 2540 PLT entries, 2227 for local syms (87%), 0 users

GCC:

  $ ~/bin/relinfo.pl qtbase/lib/libQt6Core.so.6.4.0
  qtbase/lib/libQt6Core.so.6.4.0: 6300 relocations, 5343 relative (84%), 318 PLT entries, 1 for local syms (0%), 0 users
  $ size qtbase/lib/libQt6Core.so.6.4.0
     text    data     bss     dec     hex filename
  6019871   75896   16952 6112719  5d45cf qtbase/lib/libQt6Core.so.6.4.0
  $ ninja libQt6Core.so
  [6/6] Creating library symlink qtbase/lib/libQt6Core.so.6 qtbase/lib/libQt6Core.so
  $ ~/bin/relinfo.pl qtbase/lib/libQt6Core.so.6.4.0
  qtbase/lib/libQt6Core.so.6.4.0: 6276 relocations, 5319 relative (84%), 318 PLT entries, 1 for local syms (0%), 0 users
  $ size qtbase/lib/libQt6Core.so.6.4.0
     text    data     bss     dec     hex filename
  6020091   75672   16952 6112715  5d45cb qtbase/lib/libQt6Core.so.6.4.0

Pick-to: 6.3
Change-Id: I60749953f1a63d23d696a5a547cd924ec259ead3
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

0 files changed, 0 insertions, 0 deletions