PHP has reserved all method names with a double underscore prefix for future use

While running PHP compatibility against our codebase we had the following warnings:

Function name \__acquia_purge_manualpurge_add\" is discouraged; PHP has reserved all method names with a double underscore prefix for future use"
Function name \__acquia_purge_manualpurge_remove\" is discouraged; PHP has reserved all method names with a double underscore prefix for future use"
Function name \__acquia_purge_manualpurge_paths\" is discouraged; PHP has reserved all method names with a double underscore prefix for future use"
Function name \__acquia_purge_manualpurge_validate\" is discouraged; PHP has reserved all method names with a double underscore prefix for future use"
Function name \__acquia_purge_manualpurge_submit\" is discouraged; PHP has reserved all method names with a double underscore prefix for future use"

These should not be used but there are already single underscore functions of the same name. These functions will need new names to resolve these warnings.

As these functions explicitly include acquia_purge in the name it is unlikely that PHP will use these names hence the minor priority although once a new naming convention is decided upon the fix should be a quick find and replace eliminating any possible future issues.