msvcmaker: Define _USE_MATH_DEFINES so that M_PI and other constants are defined when including <math.h>.

Also don't generate a custom build step for the .spec file for static
libraries, since they don't have a .spec file.

The include project generates .h files from .idl files so that they
can be used when compiling the modules.

Remove all functions for which the HAVE_ define is not used anywhere.

Add _strdup, _strtoi64 _strtoui64, chsize, strdup and vsnprintf which
are all present in MSVC headers.

These defines aren't needed. Move the X_DISPLAY_MISSING and __ASM_*
defines to after the PACKAGE_* defines to match config.h.in.

Update list of headers present in the MSVC build environment. fcntl.h
isn't detected by configure and so isn't needed.

Factor out writing of common compiler settings and setting of common defines.

Factor out the writing of HAVE_* defines in include/config.h and sort
the resulting defines before writing.

msvcmaker: Fix the generated filename for the spec file for modules with extensions other than .dll.

This gets make_opengl to work again with Perl 5.10.