In OOo times, there'd originally been efforts to allow building on Windows with
MinGW.  Later, in LO times, this has been shifted to an attempt of cross-
compiling for Windows on Linux.  That attempt can be considered abandoned, and
the relevant code rotting.

Due to this heritage, there are now three kinds of MinGW-specific code in LO:

* Code from the original OOo native Windows effort that is no longer relevant
  for the LO cross-compilation effort, but has never been removed properly.

* Code from the original OOo native Windows effort that is re-purposed for the
  LO cross-compilation effort.

* Code that has been added specifially for the LO cross-compilation effort.

All three kinds of code are removed.

(An unrelated, remaining use of MinGW is for --enable-build-unowinreg, utilizing
--with-mingw-cross-compiler, MINGWCXX, and MINGWSTRIP.)

Change-Id: I49daad8669b4cbe49fa923050c4a4a6ff7dda568
Reviewed-on: https://gerrit.libreoffice.org/34127
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

Change-Id: If04d3f07dc8bffac8887773b5424c09848cd8f1a
Reviewed-on: https://gerrit.libreoffice.org/29404
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

Change-Id: Ia5c85b8e697491aafc9de4838504226f11480b44
Reviewed-on: https://gerrit.libreoffice.org/11081
Reviewed-by: Thomas Arnhold <thomas@arnhold.org>
Tested-by: Thomas Arnhold <thomas@arnhold.org>

Change-Id: I399df92d2b6907c129e18f3a55afeadf02783c14
Reviewed-on: https://gerrit.libreoffice.org/6548
Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>