update libhsl/coin-hsl prebuild packages description again

- at least libHSL already includes all dependencies
- Coin-HSL so far misses the header file to be used as buildtime, so
  it is essentially the same as libHSL (just smaller)
- both are only for macOS and Windows (for Linux, one would need to
  unpack a julia package; we skip mentioning that)
- see #721

README.md

@@ -63,7 +63,7 @@ in the Ipopt documentation. In the following, we only summarize some main points
 Ipopt requires at least one of the following solvers for systems of linear equations:
 - MA27, MA57, HSL_MA77, HSL_MA86, or HSL_MA97 from the [Harwell Subroutines Library](http://hsl.rl.ac.uk) (HSL).
   It is recommended to use project [ThirdParty-HSL](https://github.com/coin-or-tools/ThirdParty-HSL) to build a HSL library for use by Ipopt
-  or to use [prebuild libraries from STFC](https://licences.stfc.ac.uk/product/libhsl), see the [Ipopt installation instruction](https://coin-or.github.io/Ipopt/INSTALL.html#DOWNLOAD_HSL).
+  or to use [prebuild macOS/Windows libraries from STFC](https://licences.stfc.ac.uk/product/libhsl), see the [Ipopt installation instruction](https://coin-or.github.io/Ipopt/INSTALL.html#DOWNLOAD_HSL).
 - [Parallel Sparse Direct Linear Solver](http://www.pardiso-project.org) (Pardiso).
   Note, that the Intel Math Kernel Library (MKL) also includes a version of Pardiso, but the one from Pardiso Project often offers better performance.
 - [Sparse Parallel Robust Algorithms Library](https://github.com/ralna/spral) (SPRAL).

doc/install.dox

@@ -230,17 +230,11 @@ You may either:
 \attention The build system of %Ipopt currently requires that MA27 is part
 of a HSL library, if a HSL library is provided.
 
-Next to the HSL source packages, also **prebuild libraries** of HSL are
-available in the LibHSL package from https://licences.stfc.ac.uk/product/libhsl.
-They can be used by %Ipopt when using the shared library loading mechanism
+Next to the HSL source packages, also **prebuild libraries** of HSL for macOS and Windows are
+available in the libHSL package from https://licences.stfc.ac.uk/product/libhsl
+and the Coin-HSL package from https://licences.stfc.ac.uk/product/coin-hsl.
+Both can be used by %Ipopt when using the shared library loading mechanism
 described \ref LINEARSOLVERLOADER "below".
-However, there are additional dependencies that need to be downloaded as well:
-[OpenBLAS32](https://github.com/JuliaBinaryWrappers/OpenBLAS32_jll.jl/releases),
-[METIS](https://github.com/JuliaBinaryWrappers/METIS_jll.jl/releases),
-[CompilerSupportLibraries](https://github.com/JuliaBinaryWrappers/CompilerSupportLibraries_jll.jl/releases).
-
-In addition, a package of prebuild libraries specially made for use by Ipopt
-is available together with the HSL source package at https://licences.stfc.ac.uk/product/coin-hsl.
 
 \note Whereas it is essential to have at least one linear solver, the
 package MC19 could be omitted (with the consequence that you cannot use