Use $(MAKE) instead of make to fix the build if GNU make is called something else...

Use $(MAKE) instead of make to fix the build if GNU make is called something else on the system.

Original commit message from CVS:
* check.mak:
* coverage/lcov.mak:
* gtk-doc-plugins.mak:
* release.mak:
Use $(MAKE) instead of make to fix the build if GNU make is called
something else on the system.
* m4/as-docbook.m4:
Fix path for docbook.xsl if we have no /etc/xml/catalog and add a
docbook-xsl search path for FreeBSD.