Vips: make core deps recommended

libvips has a lot of dependencies: some are used to implement core
functions, some are used to add support for less-used file formats.
Previously all non-required dependencies were :optional, so, by default,
libvips was missing a lot of features.

This patch tags dependencies which are used to implement vips operations
and support for common file formats as :recommended and leaves those
which are used for less-common file formats as :optional.

Closes #707.
Scalapack: add head.
Mumps: select compiler based on :mpi.
Ipopt: Upgrade to 3.11.7 and build fixes.

- Remove MPI compilers from environment as they crash the linker
- Apply patch if Mumps was built in parallel
- Add option to skip build-time tests.

Closes #656.
Catch up with upstream audit changes
ipopt: don't do work in class scope
"--universal" is propagated automatically to deps that define it
spatialite-gis: remove conflicting LDFLAG

Closes #709.
igraph 0.7.0

Update homepage to http://igraph.org.

Closes #711.
igraph: add test
gmt 4.5.12

Closes #712.
gmt 5.1.1

Add conflicts_with GMT 4, provided by gmt4 formula.
GMT build system has now moved to cmake.

Closes #473.
gmt4: move GMT 4 to new formula

Add conflicts_with current gmt.
Prior history for GMT 4 formulae preserved in gmt.rb
Batch convert http download urls from SourceForge to https

Corresponds to upstream audit changes. See Homebrew/homebrew#27041
fastx_toolkit: use resources
lp_solve: use resources
samtools: use resource
snid: use resources
openimageio: use resources
fwdpp 0.2.0 (new formula)

The 'fwdpp' template library abstracts the basic operations
required to implement forward-time simulations of population-
and quantitative-genetic models.

Closes #695.