[PATCH] INSTALL documentation update for 1.9

Hi,

attached is a suggested patch/update for the INSTALL documentation for 1.9.
Given Bert's statement about the compatibility with VS 2002/2003 I
thought it might be good to also update these statements in the docu,
because they just sound rather outdated then to me.
Compared to the 1.10-patch the only difference is that I dropped the
TODO-section regarding Serf (since I thought it might be better not to
add an unfinished section rather than adding some placeholder
documentation in an already published version):

[[
Several updates/corrections to the INSTALL file:
- updated compatibility statements for Visual Studio (dropping 2002/2003
support, adding support for 2008+ versions)
- case-correction for February
- replaced dead-link to Platform SDK for VC6 with link to still
available instructions
- replaced redirection URL zlib.org with direct URL zlib.net
- update VS build instructions to be suitable for VS >= 2010
- libmagic marked as optional dependency
- made URLs consistently use a trailing /
- corrected minimum Serf version (1.2.1 -> 1.3.4)
- corrected section numbering and referencing in several cases
- clarify that Python is required for Windows as well
- specify Python >= 3.0 being unsupported atm
- dropping explicit mentioning of Subversion version 1.8 (since the
documentation always applies to the current version)
- added missing prerequisite an install step instruction for SQLite 3.7.12
- added optional-markers to steps which are not required in all cases
- clarified when serf is required
- replaced DRIVE-variable with BUILD_ROOT-variable to make things a bit
easier to understand
- added missing required quotes around SDK-paths which contain spaces
- added sections about building APR and ZLib to give some leads how to
build these from source

* INSTALL
     documentation updated
]]]

Regards,
Stefan