Check presence of ld.so.conf files. Add support of additional ld.so.conf in /opt path

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branch : ld_so_conf
added a buildinput command to add additional input dependencies to custom build commands.

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branch : custom_build_additional_inputs
added support for buildinputs in vs200x generators

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branch : custom_build_additional_inputs
fixed the vs201x generator (was using a space instead of a semi-colon)

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branch : custom_build_additional_inputs
added buildinputs support to make action

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branch : custom_build_additional_inputs
updated buildinputs tests to check the file separator

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branch : custom_build_additional_inputs
Fix bootstrapping with premake4
Fix per-file custom build commands in C++ gmake action

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branch : assassini/fix-perfile-custom-build-commands-in-c-g-1411831836712
Merged in assassini/premake-dev-1/assassini/fix-perfile-custom-build-commands-in-c-g-1411831836712 (pull request #133)

Fix per-file custom build commands in C++ gmake action
Fix unit tests broken by previous commit

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branch : assassini/fix-perfile-custom-build-commands-in-c-g-1411831836712
Merge unit test fixes to previous commit
Merged in noresources/premake-dev-ns/ld_so_conf (pull request #134)

Fix error on linux if ld.so.conf does not exists
Merged in dcourtois/premake-dev/custom_build_additional_inputs (pull request #131)

added a buildinput command to add additional input dependencies to custom build commands.