Adds code folding for conditionals and support for bmake features

This is a series of commits:

makefile.xml: Allow "+" in variable names

This is used in FreeBSD lib/Makefile:SUBDIR_DEPEND_libc++:= libcxxrt

makefile.xml: initial support for bmake

makefile.xml: highlight bmake variable modifiers

makefile.xml: highlight bmake conditional expressions

makefile.xml: increase version number

makefile.xml: add code folding for bmake .if/.elif/.endif

makefile.xml: allow multiline conditionals

makefile.xml: highlight numbers in bmake conditionals

makefile.xml: highlight intentifiers in bmake conditionals as variables

makefile.xml: add support for special bmake targets such as .PHONY

makefile.xml: add support for special bmake sources such as .WAIT

makefile.xml: Add missing highlight and folding for .else

makefile.xml: add support for bmake include statement

makefile.xml: add support for bmake .info .warning and .error

makefile.xml: highlight bmake .for/.endfor and add folding

makefile.xml: highlight the remaining bmake directives

makefile.xml: add folding to GNU make conditionals and updated test

also shared some common rules