doc update: add notes about gmake options and settings.mk usage
package cfitsio: update checksum
doc update: add notes about $(TARGET)/bin in $PATH and clean environment
Improve naming of issue tracker and mailing list
Add menu entry for the issue tracker
mxe-activate: clear env vars on make invocation
mxe-activate: unset env vars for interactive use
mxe-activate: get targets from Makefile