Avoid VCL_DLLPUBLIC SolarMutexGuard "taking over" template base class on MSVC

...and thus exporting osl::Guard<comphelper::SolarMutex> members from vcl.  With
--disable-pch that caused linking Library_acc to fail with duplicate symbols, as
accessibility/source/standard/vclxaccessiblebutton.cxx uses
comphelper::OExternalLockGuard (include/comphelper/accessiblecontexthelper.hxx),
which also derives from osl::Guard<comphelper::SolarMutex> (and is also all-
inline, and not marked as DLLPUBLIC), so also emits such members.  With
--enable-pch, vclxaccessiblebutton.cxx happens to see SolarMutexGuard from
include/vcl/svapp.hxx before comphelper::OExternalLockGuard, and thus doesn't
emit any such members.

As SolarMutexGuard is all-inline, there should not be much point in making it
VCL_DLLPUBLIC in the first place (was there ever since the class's introduction
in b450a328 "create a class SolarMutexGuard to
take a Guard on the SolarMutex"), so just drop that.

Change-Id: Ie9d493370c7d34981bb35e5d9e100cf987eb83ca
Reviewed-on: https://gerrit.libreoffice.org/42616Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

include/vcl/svapp.hxx

@@ -1398,7 +1398,7 @@ private:
     DECL_STATIC_LINK( Application, PostEventHandler, void*, void );
 };
 
-class VCL_DLLPUBLIC SolarMutexGuard
+class SolarMutexGuard
     : public osl::Guard<comphelper::SolarMutex>
 {
 public:

ucb/Library_ucpimage.mk

@@ -20,6 +20,7 @@ $(eval $(call gb_Library_use_externals,ucpimage, \
 ))
 
 $(eval $(call gb_Library_use_libraries,ucpimage, \
+    comphelper \
     cppu \
     cppuhelper \
     sal \

winaccessibility/Library_uacccom.mk

@@ -56,6 +56,7 @@ $(eval $(call gb_Library_add_ldflags,UAccCOM,\
 
 $(eval $(call gb_Library_use_libraries,UAccCOM,\
 	vcl \
+	comphelper \
 	cppu \
 	sal \
 ))

winaccessibility/Library_winaccessibility.mk

@@ -52,6 +52,7 @@ $(eval $(call gb_Library_use_externals,winaccessibility,\
 
 $(eval $(call gb_Library_use_libraries,winaccessibility,\
 	UAccCOM \
+	comphelper \
 	cppu \
 	cppuhelper \
 	vcl \