Compilation problem, pnglibconf.h exists but not detected ?

Hi,

When building LibreOffice on my RHEL6 system, it successfully passed 
configure, however after lots of compiling I still get:

----
  CC     cairo-png.lo
In file included from cairo-png.c:46:
/home/dag/home-made/libreoffice/workdir/unxlngx6.pro/UnpackedTarball/png/png.h:434:27: 
error: pnglibconf.h: No such file or directory
cairo-png.c: In function ‘write_png’:
cairo-png.c:248: error: implicit declaration of function 
‘png_set_packswap’
cairo-png.c:248: warning: nested extern declaration of ‘png_set_packswap’
cairo-png.c:268: error: implicit declaration of function ‘png_set_bKGD’
cairo-png.c:268: warning: nested extern declaration of ‘png_set_bKGD’
cairo-png.c:273: error: implicit declaration of function 
‘png_convert_from_time_t’
cairo-png.c:273: warning: nested extern declaration of 
‘png_convert_from_time_t’
cairo-png.c:274: error: implicit declaration of function ‘png_set_tIME’
cairo-png.c:274: warning: nested extern declaration of ‘png_set_tIME’
cairo-png.c:284: error: implicit declaration of function 
‘png_set_write_user_transform_fn’
cairo-png.c:284: warning: nested extern declaration of 
‘png_set_write_user_transform_fn’
cairo-png.c:287: error: implicit declaration of function ‘png_set_filler’
cairo-png.c:287: warning: nested extern declaration of ‘png_set_filler’
cairo-png.c:287: error: ‘PNG_FILLER_AFTER’ undeclared (first use in this 
function)
cairo-png.c:287: error: (Each undeclared identifier is reported only once
cairo-png.c:287: error: for each function it appears in.)
cairo-png.c: In function ‘stdio_write_func’:
cairo-png.c:319: error: implicit declaration of function ‘png_error’
cairo-png.c:319: warning: nested extern declaration of ‘png_error’
cairo-png.c: In function ‘read_png’:
cairo-png.c:562: error: implicit declaration of function ‘png_read_info’
cairo-png.c:562: warning: nested extern declaration of ‘png_read_info’
cairo-png.c:574: error: implicit declaration of function 
‘png_set_palette_to_rgb’
cairo-png.c:574: warning: nested extern declaration of 
‘png_set_palette_to_rgb’
cairo-png.c:579: error: implicit declaration of function 
‘png_set_expand_gray_1_2_4_to_8’
cairo-png.c:579: warning: nested extern declaration of 
‘png_set_expand_gray_1_2_4_to_8’
cairo-png.c:587: error: implicit declaration of function 
‘png_set_tRNS_to_alpha’
cairo-png.c:587: warning: nested extern declaration of 
‘png_set_tRNS_to_alpha’cairo-png.c:590: error: implicit declaration of 
function ‘png_set_strip_16’
cairo-png.c:590: warning: nested extern declaration of ‘png_set_strip_16’
cairo-png.c:593: error: implicit declaration of function ‘png_set_packing’
cairo-png.c:593: warning: nested extern declaration of ‘png_set_packing’
cairo-png.c:599: error: implicit declaration of function 
‘png_set_gray_to_rgb’
cairo-png.c:599: warning: nested extern declaration of 
‘png_set_gray_to_rgb’
cairo-png.c:603: error: implicit declaration of function 
‘png_set_interlace_handling’
cairo-png.c:603: warning: nested extern declaration of 
‘png_set_interlace_handling’
cairo-png.c:605: error: ‘PNG_FILLER_AFTER’ undeclared (first use in this 
function)
cairo-png.c:627: error: implicit declaration of function 
‘png_set_read_user_transform_fn’
cairo-png.c:627: warning: nested extern declaration of 
‘png_set_read_user_transform_fn’
cairo-png.c:657: error: implicit declaration of function ‘png_read_image’
cairo-png.c:657: warning: nested extern declaration of ‘png_read_image’
cairo-png.c:658: error: implicit declaration of function ‘png_read_end’
cairo-png.c:658: warning: nested extern declaration of ‘png_read_end’
make[3]: *** [cairo-png.lo] Error 1
make[2]: *** [all] Error 2
make[1]: *** 
[/home/dag/home-made/libreoffice/workdir/unxlngx6.pro/ExternalProject/cairo/build] 
Error 1
make: *** [build] Error 2
----

Even when pnglibconf.h exists in the tree:

----
[dag@moria libreoffice]$ find . -name pnglibconf.h
./libpng/configs/pnglibconf.h
----

Known problem ?
--
-- dag wieers, dag@wieers.com, http://dag.wieers.com/
-- dagit linux solutions, contact@dagit.net, http://dagit.net/

[Any errors in spelling, tact or fact are transmission errors]