2014-01-22: bootstrap: also adhere to the configure parameter for guile when

bootstrap: also adhere to the configure parameter for guile when compiling the repl.

diff --git a/bootstrap.sh b/bootstrap.sh
--- a/bootstrap.sh
+++ b/bootstrap.sh
@@ -32,6 +32,6 @@ echo parsing the spec file...
 mkdir -p language/wisp
 ${guile} wisp.scm ${srcdir}/wisp-reader.w 2>/dev/null > language/wisp/spec.scm \
     && echo ...precompiling the spec file... \
-    && guile -L . -s language/wisp/spec.scm \
+    && ${guile} -L . -s language/wisp/spec.scm \
     && echo ...succeeded \
-    && echo 'to use wisp at the REPL, run `guile -L . --language=wisp`'
+    && echo to use wisp at the REPL, run '`'${guile} -L . --language=wisp'`'