add map example to toUpper
add std.algorithm.sum links
improve doc on std.array.join
doc std.algorithm.fill
Merge pull request #2814 from WalterBright/algo-fill-doc

document std.algorithm.fill better
Merge pull request #2805 from WalterBright/toupper-ex

add map example to toUpper
Merge pull request #2813 from WalterBright/array-join-doc

improve doc on std.array.join
std.algorithm homonym docs need improvement
Merge pull request #2815 from WalterBright/alg-doc-homonym

std.algorithm homonym docs need improvement
Merge pull request #2812 from WalterBright/sum-doc

add std.algorithm.sum documentation links