Sækja Rtools 4.5.6768

Distributed as rtools45-6768-6492.exe and rtools45-aarch64-6768-6492.exe.
Package muparser has been added and muparser support has been enabled in gdal (thanks to Chris Toney).
Upsteam MXE changesd hav been merged from 9e83f9c12e0f9e3de2d3f90bc2656cd7cce1cf0b and additional packages have been updated as below:
armadillo 15.0.3 to 15.2.3
brotli 1.1.0 to 1.2.0
c-ares 1.34.5 to 1.34.6
curl 8.16.0 to 8.18.0
freeglut 3.6.0 to 3.8.0
gdal 3.11.4 to 3.12.1
gdk-pixbuf 2.44.3 to 2.44.4
geos 3.13.1 to 3.14.1
glib 2.86.0 to 2.86.3
gnutls 3.8.10 to 3.8.11
harfbuzz 12.1.0 to 12.3.0
lcms 2.17 to 2.18
libarchive 3.8.1 to 3.8.5
libdeflate 1.24 to 1.25
libgit2 1.9.1 to 1.9.2
libgpg_error 1.56 to 1.58
libgsf 1.14.53 to 1.14.55
libpng 1.6.50 to 1.6.54
libsodium 1.0.20 to 1.0.21
libtasn1 4.20.0 to 4.21.0
libzmq 7a7bfa1 to 900a548
nettle 3.9.1 to 3.10.2
nghttp2 1.67.1 to 1.68.0
openblas 0.3.30 to 0.3.31
pcre2 10.46 to 10.47
poppler 25.10.0 to 26.01.0
proj 9.7.0 to 9.7.1
quantlib 1.39 to 1.41
sqlite 3500400 to 3510200
xz 5.8.1 to 5.8.2
zstd 1.5.7 to 1.5.7-kernel
These packages have been added:
muparser 2.3.5