Fix implementation of HYBRID_MALLOC on Cygwin.

* src/sheap.c (bss_sbrk_buffer_end): Cast to void *.
(bss_sbrk_buffer_beg): New variable.  Use it...
* src/gmalloc.c (ALLOCATED_BEFORE_DUMPING) [CYGWIN]: ...here, to fix
  incorrect definition.
* configure.ac [CYGWIN]: Enable sound support.
Ignore files and fix indentation of else static if in d-mode
Emacs compiles after porting changes from http://cx4a.org/repo/emacs.bzr/regexp
Add flag compilation-do-echo-command