container for values.

Instead of having one evaluator function that returns a
generic Value, there is now an evaluator function for each
generalized type that simply returns a native type.

The compiler is more type-safe now because there are almost no
type conversions at evaluation time and it's impossible to
invoke a nil evaluator function during evaluation.  This also
makes ideals and pointers really clean.

As an added bonus, expression evaluation should be faster
because it doesn't require heap allocation for every
intermediate value, type switches, or lots of conversions to
and from Value.  It also involves fewer function calls.

R=rsc
APPROVED=rsc
DELTA=431  (280 added, 115 deleted, 36 changed)
OCL=31705
CL=31709

R=rsc
DELTA=23  (4 added, 7 deleted, 12 changed)
OCL=31701
CL=31703

than io.Readers and io.Writers.
change the Encoder/Decoder protocol so that each message is preceded by its length in bytes.

R=rsc
DELTA=468  (119 added, 23 deleted, 326 changed)
OCL=31700
CL=31702

R=rsc
DELTA=5  (4 added, 1 deleted, 0 changed)
OCL=31690
CL=31692

pointer types, supports literals, identifiers, type-checking
most unary and binary operators, "compiling" a few unary and
binary operators, and assignment and declaration statements.

R=rsc
APPROVED=rsc
DELTA=1751  (1751 added, 0 deleted, 0 changed)
OCL=31309
CL=31691

	1) terminate outstanding calls on the client when we see EOF from server
	2) allow data to drain on server before closing the connection

R=rsc
DELTA=41  (23 added, 4 deleted, 14 changed)
OCL=31687
CL=31689

1. use CONNECT instead of GET.
   CONNECT has exactly the meaning
   we want; most of the time people
   connect to ip:port; we're connecting
   to /_goRPC_

2. wait for a successful HTTP response
   before assuming we are connected to
   the RPC protocol.  this allows better
   error reporting and also keeps the
   protocol alternating between speakers,
   so that the buffering in the HTTP request
   reader cannot accidentally eat some
   RPC bytes too.

gotest sometimes hangs, but not in HTTP.

gotest -match=Unknown hangs every few runs
even in a clean client.

R=r
DELTA=117  (57 added, 44 deleted, 16 changed)
OCL=31656
CL=31685

R=rsc
APPROVED=rsc
DELTA=81  (53 added, 3 deleted, 25 changed)
OCL=31651
CL=31675

R=rsc
DELTA=17  (8 added, 0 deleted, 9 changed)
OCL=31670
CL=31674

R=gri
APPROVED=gri
DELTA=5  (5 added, 0 deleted, 0 changed)
OCL=31673
CL=31673

R=rsc
APPROVED=rsc
DELTA=49  (49 added, 0 deleted, 0 changed)
OCL=31568
CL=31671

R=rsc
DELTA=159  (110 added, 29 deleted, 20 changed)
OCL=31646
CL=31652

only when there's an error.

R=rsc
APPROVED=rsc
DELTA=3  (0 added, 2 deleted, 1 changed)
OCL=31650
CL=31650

R=gri
DELTA=15  (6 added, 5 deleted, 4 changed)
OCL=31649
CL=31649

TBR=r
OCL=31647
CL=31647

R=rsc
DELTA=33  (1 added, 3 deleted, 29 changed)
OCL=31620
CL=31642

R=rsc
DELTA=16  (6 added, 1 deleted, 9 changed)
OCL=31638
CL=31641

R=austin
DELTA=42  (37 added, 5 deleted, 0 changed)
OCL=31618
CL=31633

R=rsc
APPROVED=rsc
DELTA=1543  (1528 added, 0 deleted, 15 changed)
OCL=31570
CL=31630

R=rsc
APPROVED=rsc
DELTA=26  (22 added, 1 deleted, 3 changed)
OCL=31613
CL=31629

R=rsc
APPROVED=rsc
DELTA=12  (12 added, 0 deleted, 0 changed)
OCL=31619
CL=31621

R=rsc
DELTA=186  (133 added, 20 deleted, 33 changed)
OCL=31611
CL=31616

R=rsc
APPROVED=rsc
DELTA=82  (80 added, 2 deleted, 0 changed)
OCL=31610
CL=31612

R=rsc
APPROVED=rsc
DELTA=311  (308 added, 3 deleted, 0 changed)
OCL=31569
CL=31606

and use shared error handling infrastructure

R=rsc
DELTA=109  (3 added, 86 deleted, 20 changed)
OCL=31600
CL=31605

R=rsc
DELTA=1  (0 added, 0 deleted, 1 changed)
OCL=31574
CL=31604

R=rsc
DELTA=109  (0 added, 87 deleted, 22 changed)
OCL=31573
CL=31603

- delete error handling code which is not needed anymore

R=rsc
DELTA=83  (0 added, 65 deleted, 18 changed)
OCL=31572
CL=31602

- handle //line filename:line comments in scanner
- moved error handling code used by various scanner clients
  to errors.go
- added extra tests

R=rsc
DELTA=385  (343 added, 18 deleted, 24 changed)
OCL=31551
CL=31601

R=r
DELTA=20  (0 added, 20 deleted, 0 changed)
OCL=31584
CL=31598

delay evaluation of most types (all but func)
from parse time to type check time.

R=ken
OCL=31585
CL=31585

silence gcc warning.

R=ken
OCL=31583
CL=31583

R=ken
OCL=31582
CL=31582

R=rsc
APPROVED=rsc
DELTA=61  (40 added, 18 deleted, 3 changed)
OCL=31502
CL=31580

R=rsc
APPROVED=rsc
DELTA=17  (0 added, 0 deleted, 17 changed)
OCL=31503
CL=31579

of text.

R=rsc
APPROVED=rsc
DELTA=3  (1 added, 2 deleted, 0 changed)
OCL=31575
CL=31575

R=rsc
APPROVED=rsc
DELTA=5  (4 added, 0 deleted, 1 changed)
OCL=31564
CL=31567

whether no register argument was
REGARG == 0 or REGARG < 0.
use REGARG < 0 because arm needs 0 for R0.

R=ken
OCL=31562
CL=31566

R=rsc
APPROVED=rsc
DELTA=7  (7 added, 0 deleted, 0 changed)
OCL=31563
CL=31565

runtime package for use by debugger,
which needs to make sure that all ptrace calls
about a given pid come from the same thread.

R=r
DELTA=175  (90 added, 63 deleted, 22 changed)
OCL=31546
CL=31558