fix display when reader abbreviations disabled
Fix language config dialog not showing when some languages are disabled
Fixed bigfloats on Win64. Win64's long type is 32 bits and GMP's default is to
use longs for the "limbs" of bigints. However, when GMP's configure script
detects that mingw64 is compiling, it defines LONG_LONG_LIMB, which makes the
type of limbs long long, or 64 bits. This is fine; a 64-bit machine should use
64-bit ints for the digits of its bigints. It would have been nice to know
this special case earlier, though I can see why it's not advertised: most
users don't need to know, and it seems like it's obviously the right choice to
make when dealing with Win64's annoying ABI.

Made "mpfr.rkt" search for 'mpfr_set_z_exp if 'mpfr_set_z_2exp isn't found.
Hopefully this allows the bigfloat tests to finish on DrDr. If not, DrDr
will need a libmpfr upgrade.

Made some minor doc fixups
Removed fallback to 'mpfr_set_z_exp - didn't work, probably never existed
Fix TR error for missing mandatory keywords
Reimplemented `mpfr_set_z_2exp' in Racket as a fallback for older versions
of libmpfr (like DrDr's) that don't have it

Reimplemented really simple FFI functions (e.g. mpfr-prec, mpfr-exp) to
avoid calling overhead

Renamed `bigfloat-sign' to `bigfloat-signbit'

Renamed `bigfloat-sig+exp' to `bigfloat->sig+exp' (for symmetry with
`sig+exp->bigfloat')
Make srclocs serializable.
Added stress test: libmpfr C struct accessor vs. Racket struct accessor
Added `array->list-array'

Cleaned up expected value code a little

Refactored running statistics objects (hid private fields, added
`update-statistics*')

Documented expected value functions and running statistics

Removed `bfpsi0' from bigfloat tests (DrDr's libmpfr doesn't have it)

Commented out custodian shutdown callback that frees MPFR's cache
(something's broken)
avoid spurious arity mismatch in {s,n}boyer benchmarks
benchmark noise

Remove an unnecessary manual unrolling
define-logger: make `(define-logger X)' define `X-logger'
Peephole optimization for iterating over an empty set (no allocation).
ffi: fix prop:cpointer so that it works with a procedure value
Change latex render units from px (pdflatex specific) to bp (tex).

The px unit is a pdflatex specific adjustable unit that is 1 bp (big
point = 1/72in) by default.  This commit changes the latex renderer to
use bp which is a standard TeX unit equivalent to the default px
value.  This change allows .tex files generated by scribble to work
with other latex engines such as xelatex.

http://nwalsh.com/tex/texhelp/Plain.html#dimensions
http://tex.stackexchange.com/questions/41370/what-are-the-possible-dimensions-sizes-units-latex-understands

Here is a small test of using scribble and xelatex:

$ cat try.scrbl
@(require scriblib/figure redex/reduction-semantics redex/pict)
@(define-language L)
@(render-term L (term 1))

$ scribble --latex try.scrbl ; xelatex try
Increase some DrDr timeouts.
Increase another timeout.
Fixed infinite printing loop

When libmpfr wasn't available, the function created by `make-not-available'
would try to print any _mpfr arguments, which would call the custom _mpfr
printer, which would try to use a libmpfr function, which would call the
function created by `make-not-available', which would try to print...
redex-generator: correctly drop failure continuations
add some random generation tests