Force C locale in LC_NUMERIC when calling cmsGetPostScriptCSA

Otherwise we get brokenly formatted PS
7 jobs for fix_lcms_broken_ps in 2 minutes and 57 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #3449667
build

00:02:57

passed #3449672
build_android

00:01:39

passed #3449668
build_clang_libcpp

00:02:34

passed #3449671
build_clazy

00:02:00

passed #3449670
build_mingw64_fedora

00:02:30

passed #3449669
build_ubuntu_16_04

00:01:42

passed #3449666
clang_format

00:01:07