It works on Fedora gcc-c++-4.3.2-7.x86_64 but on 4.4-HEAD DIEs for DW_TAG_imported_module are just missing.

import.C
------------------------------------------------------------------------------
namespace A
  {
    int v;
  }

int
f ()
{
  using namespace A;
  return v;
}
------------------------------------------------------------------------------

g++ -c -o import.o import.C -Wall -g

From gcc-c++-4.3.2-7.x86_64:
 <1><2d>: Abbrev Number: 2 (DW_TAG_subprogram)
    <2e>   DW_AT_external    : 1        
    <2f>   DW_AT_name        : f        
    <31>   DW_AT_decl_file   : 1        
    <32>   DW_AT_decl_line   : 7        
    <33>   DW_AT_MIPS_linkage_name: (indirect string, offset: 0x37): _Z1fv      
    <37>   DW_AT_type        : <0x5b>   
    <3b>   DW_AT_low_pc      : 0x0      
    <43>   DW_AT_high_pc     : 0xc      
    <4b>   DW_AT_frame_base  : 0x0      (location list)
    <4f>   DW_AT_sibling     : <0x5b>   
 <2><53>: Abbrev Number: 3 (DW_TAG_imported_module)
    <54>   DW_AT_decl_file   : 1        
    <55>   DW_AT_decl_line   : 9        
    <56>   DW_AT_import      : <0x62>   [Abbrev Number: 5 (DW_TAG_namespace)]

From
GNU C++ (GCC) version 4.4.0 20081202 (experimental) (x86_64-unknown-linux-gnu)
	compiled by GNU C version 4.4.0 20081202 (experimental), GMP version 4.2.2, MPFR version 2.3.2.
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
 <1><2d>: Abbrev Number: 2 (DW_TAG_subprogram)
    <2e>   DW_AT_external    : 1        
    <2f>   DW_AT_name        : f        
    <31>   DW_AT_decl_file   : 1        
    <32>   DW_AT_decl_line   : 7        
    <33>   DW_AT_MIPS_linkage_name: (indirect string, offset: 0x2b): _Z1fv      
    <37>   DW_AT_type        : <0x4f>   
    <3b>   DW_AT_low_pc      : 0x0      
    <43>   DW_AT_high_pc     : 0xc      
    <4b>   DW_AT_frame_base  : 0x0      (location list)

(other DIEs exactly the same, DW_TAG_imported_module is missing here)