If a complex value is expected to be of type size_t, and the compiled
value is constant, the constant size_t value is remembered at compile
time.

The value is accessed through ngx_http_complex_value_size() which
either returns the remembered constant or evaluates the expression
and parses it as size_t.

In contrast to ngx_http_test_predicates(), it requires all values to be
non-empty and not equal to "0".

There are lots of C4244 warnings (conversion from 'type1' to 'type2',
possible loss of data), so they were disabled.

The same applies to C4267 warnings (conversion from 'size_t' to 'type',
possible loss of data), most notably - conversion from ngx_str_t.len to
ngx_variable_value_t.len (which is unsigned:28).  Additionally, there
is at least one case when it is not possible to fix the warning properly
without introducing win32-specific code: recv() on win32 uses "int len",
while POSIX defines "size_t len".

The ssize_t type now properly defined for 64-bit compilation with MSVC.
Caught by warning C4305 (truncation from '__int64' to 'ssize_t'), on
"cutoff = NGX_MAX_SIZE_T_VALUE / 10" in ngx_atosz()).

Several C4334 warnings (result of 32-bit shift implicitly converted to 64 bits)
were fixed by adding explicit conversions.

Several C4214 warnings (nonstandard extension used: bit field types other
than int) in ngx_http_script.h fixed by changing bit field types from
uintptr_t to unsigned.

secure_link_expires