By default, "map" creates cacheable variables [1].  With this
parameter it creates a non-cacheable variable.

An original idea was to deduce the cacheability of the "map"
variable by checking the cacheability of variables specified
in source and resulting values, but it turned to be too hard.
For example, a cacheable variable can be overridden with the
"set" directive or with the SSI "set" command.  Also, keeping
"map" variables cacheable by default is good for performance
reasons.  This required adding a new parameter.

[1] Before db699978a33f (1.11.0), the cacheability of the
"map" variable could vary depending on the cacheability of
variables specified in resulting values (ticket #1090).
This is believed to be a bug rather than a feature.

No functional changes.

Resolved warnings about declarations that hide previous local declarations.
Warnings about WSASocketA() being deprecated resolved by explicit use of
WSASocketW() instead of WSASocket().  When compiling without IPv6 support,
WinSock deprecated warnings are disabled to allow use of gethostbyname().

Casts between pointers and integers produce warnings on size mismatch.  To
silence them, cast to (u)intptr_t should be used.  Prevoiusly, casts to
ngx_(u)int_t were used in some cases, and several ngx_int_t expressions had
no casts.

As of now it's mostly style as ngx_int_t is defined as intptr_t.

Added variable name syntax checks to "geo" and "map" directives.

The "include" directive should be able to include multiple files if
given a filename mask.  Fixed this to work for "include" directives
inside the "map" or "types" blocks.  The "include" directive inside
the "geo" block is still not fixed.

Previous code incorrectly used ctx->var_values as an array of pointers to
ngx_http_variable_value_t, but the array contains structures, not pointers.
Additionally, ctx->var_values inspection failed to properly set var on
match.