Updated date to April 2.

	modified:   doc/libdwarf.dox
	modified:   doc/libdwarf.pdf
Added fuller explanation of the use of
shell envronment variable 'DWARF_WHICH_ALLOC'
to influence the use of malloc() vs mmap().
mmap() is only usable (in this release) on Elf
object files.
	modified:   src/lib/libdwarf/libdwarf.h

Author: davea42

doc/libdwarf.dox

@@ -3,7 +3,7 @@
     @tableofcontents{HTML:3,LaTeX:3}
     @author David Anderson
     @copyright  This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.
-    @date 2025-03-19 v0.12.0
+    @date 2025-04-02 v0.12.0
 
     @section draft Suggestions for improvement are welcome.
 

doc/libdwarf.pdf

@@ -9868,12 +9868,13 @@ DW_API int dwarf_object_detector_fd(int dw_fd,
 
     The default allocation preference is mmap.
 
-    The environment variable DWARF_WHICH_ALLOC
+    The shell environment variable DWARF_WHICH_ALLOC
     is also involved at runtime.
     If the value is 'malloc' then use of read/malloc
     is preferred.
     If the value is 'mmap' then use of mmap is
-    preferred.
+    preferred (Example: 'export DWARF_WHICH_ALLOC=mmap').
+    Otherwise, the environment value is checked and ignored.
 
     If present and valid this environment variable
     takes precedence over