Add possibility to specify GAVL, GSA and HTIMER generated symbols scope.

Add possibility to specify GAVL, GSA and HTIMER generated symbols scope.

This allows to GSA_CUST_DEC_SCOPE declaration macro variant
where the first argument can select static scope or explicit
functions visibility
	UL_ATTR_UNUSED static
	UL_EXPORT
	UL_DLLLOCAL
	UL_DLLPUBLIC
The DLL symbol visibility macros are defined in ul_udexport.h
header file. Same GAVL, GSA and HTIMER implementation macro
is used as for case of declaration with default functions scope.