Merge big.hh and small.hh into arrays.hh

* src/arrays.hh: As stated.
* src/ply.hh: Move wlen/from here, from small.hh.

Elsewhere fix references.

Author: lloda

README.md

@@ -7,7 +7,7 @@
 
 **ra-ra** implements [expression templates](https://en.wikipedia.org/wiki/Expression_templates). This is a C++ technique (pioneered by [Blitz++](http://blitz.sourceforge.net)) to delay the execution of expressions involving array operands, and in this way avoid the unnecessary creation of large temporary array objects.
 
-**ra-ra** is compact (<5k loc), easy to extend, and generic. There are no arbitrary type restrictions or limits on rank or argument count.
+**ra-ra** is compact (≈4k loc), easy to extend, and generic. There are no arbitrary type restrictions or limits on rank or argument count.
 
 In this example ([examples/read-me.cc](examples/read-me.cc)), we create some arrays, do operations on them, and print the result.
 

TODO

@@ -175,8 +175,6 @@ Some of these aren't bugs in the sense that I expect to solve them, but more lik
   44. [ ]
   45. [ ]
   46. [ ]
-  47. [ ] ra/big.hh, test/const.cc, ra/view-ops.hh ...: Review constness in ra/view-ops.hh after the
-      Big/ViewBig const fixes after 913d6b531801609cb61bb7f631ddf50de701a802.
 
 * Old bugs or issues
   - [X] Before merging saveload [1/1]
@@ -195,7 +193,7 @@ Some of these aren't bugs in the sense that I expect to solve them, but more lik
   - [X] Error report, debugging [3/3]
     - [X] Optionally throw instead of abort on bounds checks, etc. cf. test/ra-12.cc
       * This was fixed between v8 and v10, see examples/throw.cc.
-    - [X] Static check on Small constructors e.g. real3 {1, 2, 3}. Cf big.hh:513 init<SS>(SS const & s).
+    - [X] Static check on Small constructors e.g. real3 {1, 2, 3}.
       - [X] for Container constructors
       - [X] for Small constructors
     - [X] General static check on prefix matching <2019-02-06 Wed 12:06>

box/bug83.cc

@@ -1985,10 +1985,8 @@ Generic macros, tuple library, basic types and concepts.
 Expression template nodes.
 @item @code{ply.hh} -
 Traversal, including I/O.
-@item @code{small.hh} -
-Array type with compile time dimensions.
-@item @code{big.hh} -
-Array type with run time dimensions.
+@item @code{arrays.hh} -
+Array types
 @item @code{ra.hh} -
 Functions and operators, main header.
 @item @code{test.hh} -