Hardcode couchjs binary name

Windows doesn't have the libgen.h header or an easily identified
basename function. Instead of playing games we just configure the name
with autoconf and run with that.
diff --git a/configure.ac b/configure.ac
index 182e0eb..6a5d865 100644
--- a/configure.ac
+++ b/configure.ac
@@ -127,7 +127,12 @@
 
 AC_SUBST(JS_LIB_BASE)
 
+AC_DEFINE([COUCHJS_NAME], ["couchjs"], ["CouchJS executable name."])
+
 if test x${IS_WINDOWS} = xTRUE; then
+
+    AC_DEFINE([COUCHJS_NAME], ["couchjs.exe"], ["CouchJS executable name."])
+
     if test -f "$JS_LIB_DIR/$JS_LIB_BASE.dll"; then
         # seamonkey 1.7- build layout on Windows
         JS_LIB_BINARY="$JS_LIB_DIR/$JS_LIB_BASE.dll"
diff --git a/src/couchdb/priv/couch_js/help.h b/src/couchdb/priv/couch_js/help.h
index c42c9f5..4102594 100644
--- a/src/couchdb/priv/couch_js/help.h
+++ b/src/couchdb/priv/couch_js/help.h
@@ -13,8 +13,6 @@
 #ifndef COUCHJS_HELP_H
 #define COUCHJS_HELP_H
 
-#include <libgen.h>
-
 #include "config.h"
 
 static const char VERSION_TEMPLATE[] =
@@ -55,7 +53,7 @@
     "\n"
     "Report bugs at <%s>.\n";
 
-#define BASENAME basename((char*)argv[0])
+#define BASENAME COUCHJS_NAME
 
 #define couch_version(basename)  \
     fprintf(                     \