Make packages loaded by load_all() children of global environment

[wch]

Objects loaded via load_all() behave somewhat differently from loading those loaded with library().

With load_all(), the package environment is not a child of the global environment. But with library(), it is a child of the global environment.

This code will illustrate:

# This prints all parent environments, until it hits top (emptyenv)
printenvs <- function(e = parent.frame(), n = 100) {
  cat(str(e, give.attr=F))
  i <- 1
  while(i < n) {
    if (identical(e, emptyenv()))
      break

    e <- parent.env(e)
    cat(str(e, give.attr=F))
    i <- i+1
  }
  cat("\n")
  return(e)
}


library(ggplot2)
debugonce(qplot)
qplot()
printenvs()
# <environment: R_GlobalEnv> is a parent


# === Might need to restart R to do this ===
library(devtools)
load_all('.')
debugonce(qplot)
qplot()
printenvs()
# <environment: R_GlobalEnv> is not a parent

[wch]

Implemented in #126.