REORG: config: extract the global section parser into cfgparse-global

REORG: config: extract the global section parser into cfgparse-global

The config parser is the largest file to build and its build dominates
the total project's build time. Let's start to split it into multiple
smaller pieces by extracting the "global" section parser into a new
file called "cfgparse-global.c". This removes 1/4th of the file's build
time.