support for GNU configure syntax
Correct prefix / CFG_PREFIX work in configure / install.mk
support for GNU configure syntax corrections: patch from brson
syntax: Forbid non-string literals in meta items. #623
Make Writer::flush a no-op default method

Closes #9126
Forbid type parameters in inner statics

Closes #9186
auto merge of #10164 : brson/rust/configure, r=brson

Rebase of #9990
auto merge of #10166 : brson/rust/meta, r=alexcrichton

This doesn't fix #623 but works around it by limiting the grammar.
auto merge of #10180 : alexcrichton/rust/flush-default, r=brson

Closes #9126
Fix missing parenthesis in a previous substitution '$(PREFIX_ROOT)' to  '$(CFG_MANDIR' on 1c4a348b072a
auto merge of #10189 : alexcrichton/rust/inner-statics, r=cmr

Closes #9186
auto merge of #10193 : osaut/rust/Fix_install, r=huonw

Fix missing parentheses coming from a previous substitution '$(PREFIX_ROOT)' to  '$(CFG_MANDIR' on 1c4a348b072a