Update to 0.2.5

Build now explicitly requires gmake

per https://github.com/yaml/libyaml/releases/tag/0.2.5
the following changes have been made

• #105 Allow question marks in plain scalars in flow collections

• #186 Emitter: Don't output trailing space for empty scalar nodes

• #185 Emitter: Output space after an alias mapping key

• #187 Add -h and --flow (on|off|keep) to run-*-test-suite

• #182 Remove unnecessary include and malloc

• #177 Add specific files back to .gitignore

• #181 Output error position in run-parser-test-suite.c

• #191 A couple patches to improve test suite support

• #179 Flow indicators can not be part of local or shorthand tags

PR: 247043
Submitted by: daniel.engberg.lists@pyret.net