Optimize PW compact

[Kalashnikovni]

Currently a PW like the following one is not compacted:

<<{[109:998]} -> |x-109|, {[108:108]} -> |x-108|, {[107:107]} -> |x-107|, {[106:106]} -> |x-106|, {[105:105]} -> |x-105|, {[104:104]} -> |x-104|, {[103:103]} -> |x-103|, {[102:102]} -> |x-102|, {[101:101]} -> |x-101|, {[100:100]} -> |x-100|, {[0:99], [999:999]} -> |x|, {[2000:2999]} -> |x-2000|, {[1000:1999]} -> |x-1000|, {[4000:4999]} -> |x-4000|, {[3000:3999]} -> |x-3000|, {[5000:5999]} -> |x-5000|, {[6990:7879]} -> |x-6990|, {[6100:6989]} -> |x-6100|, {[6000:6099]} -> |x-5900|>>

However, some sections:

{[109:998]} -> |x-109|, {[108:108]} -> |x-108|, {[107:107]} -> |x-107|, {[106:106]} -> |x-106|, {[105:105]} -> |x-105|, {[104:104]} -> |x-104|, {[103:103]} -> |x-103|, {[102:102]} -> |x-102|, {[101:101]} -> |x-101|, {[100:100]} -> |x-100|

could be compacted to:

{[100:109]} -> |0|, {[110:998]} -> |x-109|