fix our pari Makefile.in so it doesn't mask error return codes

from pari's Configure script
Merge branch 'master' of github.com:Macaulay2/M2
amend INSTALL for cygwin
Merge branch 'master' of github.com:Macaulay2/M2
Added new function 'antipode' to handle transpose of a matrix

over rings with skew commuting variables.
update INSTALL instructions for Mac OS X
Merge remote-tracking branch 'm2/master' into linalg

Conflicts fixed:
	M2/Macaulay2/m2/exports.m2