bump version for various easyconfigs that use GCCcore/6.4.0

[boegel]

In preparation of EasyBuild v3.4.0 that will include the 2017b toolchains (#4618, #4768), I think it makes sense to do an update sweep of the easyconfigs that use GCCcore/6.4.0 as toolchain that are currently included in develop (most of them contributed by @JackPerdue).

We usually don't do in-place version bumps, but since this only affects develop (none of the easyconfigs touched here have been included in an EasyBuild release), I feel this is OK (by means of exception).

• expat: 2.2.4 (was 2.2.1)
• fontconfig: 2.12.4 (was 2.12.1)
  • this was the main trigger, 2.12.1 was released Aug 5th 2016, 2.12.4 is from July 5th 2017)
• libpng: 1.6.32 (was 1.6.30)
• CMake: 3.9.1 (already there)
  • easyconfig for CMake 3.8.2 that was added in {devel}[GCCcore/6.4.0] CMake v3.8.2 #4884 is removed
• cURL: 7.55.1 (was 7.54.1)
• Eigen: 3.3.4 with dummy
  • easyconfigs with non-dummy toolchain don't make sense for Eigen (headers only, so the one added in {math}[GCCcore/6.4.0] Eigen v3.3.4 #4928 was removed)
• FreeXL: 1.0.3 (was 1.0.2)
• libsodium: 1.0.13 (was 1.0.12)
• Tcl: 8.6.7 (was 8.6.6)

Worth mentioning: #5072 also includes a couple of version bumps (Tcl 8.6.7, SQLite 3.20.1, libyaml 1.0.7), they're included there because they're (indirect) deps for the Python-core easyconfig.

[boegel]

Test report by @boegel
SUCCESS
Build succeeded for 13 out of 13 (13 easyconfigs in this PR)
node2007.delcatty.os - Linux centos linux 7.3.1611, Intel(R) Xeon(R) CPU E5-2670 0 @ 2.60GHz, Python 2.7.5
See https://gist.github.com/103da45922b10225c1dafc31d19e7814 for a full test report.

[boegel]

Test report by @boegel
SUCCESS
Build succeeded for 13 out of 13 (13 easyconfigs in this PR)
node2419.golett.os - Linux centos linux 7.3.1611, Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz, Python 2.7.5
See https://gist.github.com/96a34c403369f92c416fb3084f5470d1 for a full test report.