* name bootstrap script bootstrap as well as other xrdp repos
* use pkg-config to get pulseaudio version and module directories
* guess prefix by checking for pulseaudio executable
* simplify message then PULSE_DIR not specified
  as m4_text_box doesn't support multiple lines

so our modules will be installed where system's pulseaudio modules are.
Unfortunately, pulseaudio don't check `/usr/local` first