The idea is to use libo_MINGW_CHECK_DLL for libs that must be available
(typically that would be the "main" library, e.g., libxml2 or libcurl)
and libo_MINGW_TRY_DLL for possible dependencies (that may not be the
same on different systems). All further references to the dlls are
exclusively through the configured variables or defines set from these
variables (e.g., instead of hardcoding libxml2-2.dll, use
$(MINGW_LIBXML2_DLL)).

The macros are documented in m4/mingw.m4 .

Files that must be changed when adding a new dll:
* configure.in
* config_host.mk.in
* external/mingw-dlls/makefile.mk
* scp2/source/ooo/makefile.mk
* scp2/source/ooo/mingw_dlls.scp

Use GG era abbreviation in one format instead of full GGG.

Hopefully this will allow pasting to external applications with whole
column/row selected while not affecting calc itself.

These two tests are not well designed and need 5 and 10 minute just to
check that we really return every row. This is not a good trade-off
between test coverage and execution time.

Enable them again with a better concept.

added Info-ZIP lincense

a13a88bd changes them to build
without exceptions by mistake, causing a boost problem

The cppu::ImplInheritanceHelper1 ctor should not get instantiated, but MSVC2008
does so and then it fails to compile.

This brings down the reload time from 22 seconds to 4.3 seconds with
my test document.  This is what I've been looking for!