win32: consolidate executable handling in popen.c

Commit f444dc586 (win32: only search PATH for compressor) made
mingw_fork_compressor() perform a PATH lookup for the xz and lzma
compression programs.  This avoided relying on CreateProcess() to
perform the search.

Other callers of the pipe creation code should also avoid reliance
on CreateProcess's executable search:

- Move the applet test and PATH lookup into mingw_popen_internal().
  The first argument to CreateProcess() will always be a path to
  an executable.

- mingw_fork_compressor() uses the new "w+" mode to indicate that
  xz and lzma compressors should be found on PATH.

- mingw_popen() no longer needs to check for an applet itself, as
  that's now handled in mingw_popen_internal().

- spawn_ssl_client() in 'wget' can rely on the popen code to look
  up the 'ssl_client' applet.

- Remove unnecessary argument checks in mingw_popen_internal().

Adds 0-24 bytes.

0 files changed, 0 insertions, 0 deletions