fix Issue 11171 - text relocations in shared phobos library

- Read-only data with relocations cannot be added to CDATA,
  because text relocations are prohibited by many security
  checks (SELinux).
  Also text relocations effectively break sharing of
  read-only segments across multiple processes.
use .data.rel.ro segment for constant data with relocations

- The runtime linker will mark this as read only
  after relocations are processed.
Merge pull request #3187 from MartinNowak/fix11171

[dll] fix Issue 11171 – Text relocations in Phobos shared library
Revert "Merge pull request #3209 from 9rnsr/fix11939"

This reverts commit 931c72761178a224d44798813ff2667d7fb13e46, reversing
changes made to 3f5d722f6dbca011c60c3282d88ec024d6c06709.

Because it's incorrectly merged change.
Merge pull request #3241 from 9rnsr/RevertPull3209

Revert "Merge pull request #3209 from 9rnsr/fix11939"