Remove $Core and $Mod* comments apart from $ModDep.
Remove detection of deprecated backticks which was added in 1.1b9.
Fix $ModDep failing to find application-wide include files.
Fix some missing newlines in the config header generator.
Fix users being able to set <server:network> to an invalid value.
Merge pull request #580 from SaberUK/master+restrict-network-name

Fix users being able to set <server:network> to an invalid value.
Merge pull request #574 from SaberUK/master+build-comment-cleanup

Clean up unneeded build system comments.
Remove support for Interix and SunOS from the Makefile.

- SunOS was replaced with Solaris in 1992(!).
- We have a native Windows port so Interix is not needed.
Tidy up CXXFLAGS and LDFLAGS.

- Add -Iinclude at declaration instead of doing it later on.
- Add -Wextra -Wfatal-errors and -Wno-unused-parameter.
- Enable -Wall and -Wshadow on ICC.
- Remove -DPIC (useless).
- Remove empty declaration of LDFLAGS.
- Remove unneeded CXXFLAGS on Darwin.
Remove 'make squeakyclean'.

This was a non-standard alias for make distclean.
Add IFNEQ Makefile template macro.

- Use template macro for ICC check.
- Don't link against pthread on Darwin.
Use CXX instead of CC.

CXX is the correct variable to use as CC is the C compiler.
Rename CXXFLAGS to CORECXXFLAGS to respect users enviroment.
Merge pull request #577 from SaberUK/master+makefile-cleanup

Tidy up the Makefile template.
Purge --with-cc in favour of the CXX environment variable.
Automatically detect the compiler which the user has installed.
Correctly detect the compiler version and whether it is acceptable.
Rename configuration variable to CXX to match everything else.
Expose compiler name to make.

- Use libc++ when building on Darwin instead of libstdc++.
- Convert ICC detection to use new variable.