Got rid of the requirement to have a "package" directive. Fixed a grammar error

found in the process. Also taught the regression test system a new trick: the
path to "fped" can be passed in the environment variable FPED. E.g.,
FPED=fped.r5943 make test

- fped.c (usage, main): duplicating the -T option produces a dump to stdout
  before exiting (like %dump would)
- test/Common: new command fped_dump to invoked fped with a second -T option
- test/Common: if the environment variable FPED is set, use its content to
  invoke fped (default is ../fped)
- test/Common: if the environment variable CWD_PREFIX is set, prepend it to
  $FPED if the latter is a relative path 
- Makefile (test, tests): set CWD_PREFIX to .., so that the path given in FPED
  is valid at the point of invocation
- fpd.y: revised grammar to make "package" optional
- fpd.y: measurements were syntactically allowed inside non-root frame
  (test/structure)
- test/structure: test various combinations of the grammatical file structure
- test/tsort: removed all the now unnecessary "package" directives



git-svn-id: http://svn.openmoko.org/trunk/eda/fped@5944 99fdad57-331a-0410-800a-d7fa5415bdb3

README

@@ -148,6 +148,8 @@ unit mm
 unit mil
 unit auto
 
+If the "unit" directive is omitted, fped defaults to millimeters.
+
 When saving a footprint definition, the default unit is set to the
 unit set in the GUI.
 
@@ -301,8 +303,9 @@ meas a b 0.2 mm
 Package name
 - - - - - -
 
-The package name is a string of printable ASCII characters, including
-spaces.
+The package name is a non-empty string of printable ASCII characters,
+including spaces. If the "package" directive is omitted, fped defaults
+to using the name "_".
 
 package "<name>"